| **LOANS AND ALLOWANCE FOR CREDIT LOSSES (Tables)**              | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    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| **Loans and Leases Receivable Disclosure [Abstract]**           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            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| Schedule of Loans Receivable                                    | The following table presents the composition of the gross loans held for investment by type of loan and by fixed and variable rates at the dates indicated: September 30, 2015 December 31, 2014 Amount Percent Amount Percent (dollars in thousands)Commercial loans held for investment:       Commercial real estate loans$8,495,182 10.8% $8,739,233 11.5%Commercial and industrial loans19,361,751 24.6% 17,092,312 22.5%Multi-family loans9,600,527 12.2% 8,705,890 11.5%Other commercial(2)2,366,742 3.0% 2,084,232 2.7%Total commercial loans held for investment39,824,202 50.6% 36,621,667 48.2%Consumer loans secured by real estate:       Residential mortgages6,408,164 8.1% 6,773,575 8.9%Home equity loans and lines of credit6,155,218 7.9% 6,206,980 8.2%Total consumer loans secured by real estate12,563,382 16.0% 12,980,555 17.1%Consumer loans not secured by real estate:       Retail installment contracts and auto loans24,597,860 31.3% 22,430,241 29.5%Personal unsecured loans644,548 0.8% 2,696,820 3.5%Other consumer(3)1,079,729 1.3% 1,303,279 1.7%Total consumer loans38,885,519 49.4% 39,410,895 51.8%Total loans held for investment(1)$78,709,721 100.0% $76,032,562 100.0%Total loans held for investment:       Fixed rate$46,983,682 59.7% $45,425,408 59.7%Variable rate31,726,039 40.3% 30,607,154 40.3%Total loans held for investment(1)$78,709,721 100.0% $76,032,562 100.0%(1)Total loans held for investment includes deferred loan fees, net of deferred origination costs and unamortized purchase premiums, net of discounts as well as purchase accounting adjustments. These items resulted in a net decrease in loan balances of $193.1 million as of September 30, 2015 and a net decrease in loan balances of $1.5 billion as of December 31, 2014, respectively. (2)Other commercial primarily includes commercial equipment vehicle funding ("CEVF") leveraged leases and loans.(3)Other consumer primarily includes recreational vehicles ("RV") and marine loans.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| **Financing Receivable, Recorded Investment [Line Items]**      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   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| Schedule of Loans by Credit Quality Indicators                  | Consumer financing receivables for which credit score is a core component of the allowance model are summarized by credit score as follows:September 30, 2015        Credit Score Range(2) Retail installment contracts and auto loans(3) Percent Personal unsecured loans balance(3) Percent  (dollars in thousands)<600 $13,049,938 51.3% $405,059 16.0%600-639 4,133,831 16.3% 406,943 16.1%640-679 3,080,110 12.1% 1,071,993 42.4%N/A(1) 5,159,734 20.3% 644,744 25.5%Total $25,423,613 100.0% $2,528,739 100.0%(1)Consists primarily of loans for which credit scores are not considered in the ALLL model.(2)Credit scores updated quarterly.(3)RICs and Personal unsecured loans include $825.8 million and $1.9 billion, respectively of LHFS at September 30, 2015 that do not have an allowance.December 31, 2014        Credit Score Range(2) Retail installment contracts and auto loans(3) Percent Personal unsecured loans balance Percent  (dollars in thousands)<600 $11,731,114 52.2% $479,537 17.8%600-639 4,071,918 18.1% 440,476 16.3%640-679 4,066,539 18.1% 1,135,068 42.1%N/A(1) 2,606,094 11.6% 641,739 23.8%Total $22,475,665 100.0% $2,696,820 100.0%(1)Consists primarily of loans for which credit scores are not considered in the ALLL model.(2)Credit scores updated quarterly.(3)RICs include $45.4 million of LHFS at December 31, 2014 that do not have an allowance.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         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| Allowance for Credit Losses by Portfolio Segment                | The activity in the ACL by portfolio segment for the three-month and nine-month periods endedSeptember 30, 2015 and 2014 was as follows: Three-Month Period Ended September 30, 2015 Commercial Consumer Unallocated Total (in thousands)Allowance for loan and lease losses, beginning of period$414,462 $2,584,404 $71,592 $3,070,458Provision for/ (Recovery of) loan losses4,824 875,614 (26,258) 854,180Charge-offs(45,440) (1,488,291) — (1,533,731)Recoveries25,091 496,348 — 521,439Charge-offs, net of recoveries(20,349) (991,943) — (1,012,292)Allowance for loan and lease losses, end of period$398,937 $2,468,075 $45,334 $2,912,346        Reserve for unfunded lending commitments, beginning of period$137,641 $— $— $137,641Provision for unfunded lending commitments— — — —Loss on unfunded lending commitments— — — —Reserve for unfunded lending commitments, end of period137,641 — — 137,641Total allowance for credit losses, end of period$536,578 $2,468,075 $45,334 $3,049,987         Nine-Month Period Ended September 30, 2015 Commercial Consumer Unallocated Total (in thousands)Allowance for loan losses, beginning of period$396,489 $1,679,304 $33,024 $2,108,817Provision for/ (Recovery of) loan losses59,745 2,651,063 12,310 2,723,118Other(1)— (27,117) — (27,117)Charge-offs(96,561) (3,337,089) — (3,433,650)Recoveries39,264 1,501,914 — 1,541,178Charge-offs, net of recoveries(57,297) (1,835,175) — (1,892,472)Allowance for loan and lease losses, end of period$398,937 $2,468,075 $45,334 $2,912,346        Reserve for unfunded lending commitments, beginning of period$132,641 $— $— $132,641Provision for unfunded lending commitments5,000 — — 5,000Loss on unfunded lending commitments— — — —Reserve for unfunded lending commitments, end of period137,641 — — 137,641Total allowance for credit losses, end of period$536,578 $2,468,075 $45,334 $3,049,987Ending balance, individually evaluated for impairment(2)$56,787 $355,515 $— $412,302Ending balance, collectively evaluated for impairment342,150 2,112,560 45,334 2,500,044        Financing receivables:       Ending balance$39,824,202 $41,876,227 $— $81,700,429Ending balance, evaluated under the fair value option or lower of cost or fair value— 3,364,866 — 3,364,866Ending balance, individually evaluated for impairment(2)367,871 3,661,622 — 4,029,493Ending balance, collectively evaluated for impairment39,456,331 34,849,739 — 74,306,070(1) The "Other" amount represents the impact on the allowance for loan and lease losses in connection with SCUSA classifying approximately $1.0 billion of retail installment contracts ("RICs") as held-for-sale during the first quarter of 2015.(2) Consumer loans individually evaluated for impairment consists of loans in TDR status NOTE 5. LOANS AND ALLOWANCE FOR CREDIT LOSSES (continued) Three-Month Period Ended September 30, 2014 Commercial Consumer Unallocated Total (in thousands)Allowance for loan and lease losses, beginning of period$359,811 $1,027,044 $39,001 $1,425,856Provision for / (Recovery of) loan losses31,506 1,012,355 (10,504) 1,033,357Other(1)— (61,220) — (61,220)Charge-offs(28,680) (981,519) — (1,010,199)Recoveries8,841 408,754 — 417,595Charge-offs, net of recoveries(19,839) (572,765) — (592,604)Allowance for loan and lease losses, end of period$371,478 $1,405,414 $28,497 $1,805,389        Reserve for unfunded lending commitments, beginning of period$170,274 $— $— $170,274Provision for unfunded lending commitments(20,000) — — (20,000)Loss on unfunded lending commitments(633) — — (633)Reserve for unfunded lending commitments, end of period149,641 — — 149,641Total allowance for credit losses, end of period$521,119 $1,405,414 $28,497 $1,955,030         Nine-Month Period Ended September 30, 2014 Commercial Consumer Unallocated Total (in thousands)Allowance for loan losses, beginning of period$443,074 $363,647 $27,616 $834,337Provision for / (Recovery of) loan losses(8,990) 2,107,830 881 2,099,721Other(1)— (61,220) — (61,220)Charge-offs(81,157) (1,744,085) — (1,825,242)Recoveries18,551 739,242 — 757,793Charge-offs, net of recoveries(62,606) (1,004,843) — (1,067,449)Allowance for loan losses, end of period$371,478 $1,405,414 $28,497 $1,805,389        Reserve for unfunded lending commitments, beginning of period$220,000 $— $— $220,000Provision for unfunded lending commitments(65,000) — — (65,000)Loss on unfunded lending commitments(5,359) — — (5,359)Reserve for unfunded lending commitments, end of period149,641 — — 149,641Total allowance for credit losses, end of period$521,119 $1,405,414 $28,497 $1,955,030Ending balance, individually evaluated for impairment(2)$73,193 $135,564 $— $208,757Ending balance, collectively evaluated for impairment298,285 1,269,850 28,497 1,596,632        Financing receivables:       Ending balance$35,683,403 $39,120,473 $— $74,803,876Ending balance, evaluated under the fair value option or lower of cost or fair value(1)19,167 1,284,403 — 1,303,570Ending balance, individually evaluated for impairment(2)502,922 998,663 — 1,501,585Ending balance, collectively evaluated for impairment35,161,314 36,837,407 — 71,998,721(1)The "Other" amount represents the impact on the allowance for loan and lease losses in connection with the sale of approximately $484 million of troubled debt restructurings ("TDRs") and non-performing loans ("NPLs") classified as held-for-sale during the quarter ended September 30, 2014. |
| Schedule of Non-accrual Loans                                   | The recorded investment in non-accrual loans disaggregated by class of financing receivables is summarized as follows: September 30, 2015 December 31, 2014 (in thousands)Non-accrual loans:   Commercial:   Commercial real estate:   Corporate banking$60,450 $90,579Middle market commercial real estate38,605 71,398Santander real estate capital3,505 5,803Commercial and industrial66,023 54,658Multi-family7,319 9,639Other commercial4,365 4,136Total commercial loans180,267 236,213Consumer:   Residential mortgages184,828 231,316Home equity loans and lines of credit126,628 142,026Retail installment contracts and auto loans936,191 960,293Personal unsecured loans12,683 14,007Other consumer30,019 12,654Total consumer loans1,290,349 1,360,296Total non-accrual loans1,470,616 1,596,509    Other real estate owned ("OREO")40,692 65,051Repossessed vehicles154,056 136,136Foreclosed and other repossessed assets377 11,375Total OREO and other repossessed assets195,125 212,562Total non-performing assets$1,665,741 $1,809,071                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      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| Aging Analysis of Loan Portfolio                                | The age of recorded investments in past due loans and accruing loans greater than 90 days past due disaggregated by class of financing receivables is summarized as follows: As of September 30, 2015  30-89Days PastDue GreaterThan 90Days TotalPast Due Current TotalFinancingReceivables(1) Recorded Investment> 90 DaysandAccruing (in thousands)Commercial:            Commercial real estate:            Corporate banking $23,789 $22,015 $45,804 $2,921,976 $2,967,780 $—Middle market commercial real estate 3,964 21,190 25,154 3,940,019 3,965,173 —Santander real estate capital 659 — 659 1,561,570 1,562,229 —Commercial and industrial 28,760 38,813 67,573 19,294,178 19,361,751 —Multi-family 21,830 635 22,465 9,578,062 9,600,527 —Other commercial 7,656 3,496 11,152 2,355,590 2,366,742 —Consumer:            Residential mortgages 144,232 155,947 300,179 6,388,749 6,688,928 —Home equity loans and lines of credit 31,268 80,107 111,375 6,043,843 6,155,218 —Retail installment contracts and auto loans 2,928,878 274,777 3,203,655 22,219,958 25,423,613 —Personal unsecured loans 92,965 86,739 179,704 2,349,035 2,528,739 77,528Other consumer 36,983 39,652 76,635 1,003,094 1,079,729 —Total $3,320,984 $723,371 $4,044,355 $77,656,074 $81,700,429 $77,528(1)Financing receivables include LHFS.  As of December 31, 2014  30-89Days PastDue GreaterThan 90Days TotalPast Due Current TotalFinancingReceivables(1) RecordedInvestment> 90 DaysandAccruing (in thousands)Commercial:            Commercial real estate:            Corporate banking $18,363 $37,708 $56,071 $3,162,080 $3,218,151 $—Middle market commercial real estate 3,179 33,604 36,783 3,706,317 3,743,100 —Santander real estate capital 4,329 2,115 6,444 1,771,538 1,777,982 —Commercial and industrial 27,071 23,469 50,540 17,060,866 17,111,406 —Multi-family 13,810 5,512 19,322 8,686,568 8,705,890 —Other commercial 5,054 1,245 6,299 2,077,933 2,084,232 —Consumer:       Residential mortgages 165,270 200,818 366,088 6,603,221 6,969,309 —Home equity loans and lines of credit 36,074 86,749 122,823 6,084,157 6,206,980 —Retail installment contracts and auto loans 3,046,943 259,534 3,306,477 19,169,188 22,475,665 —Personal unsecured loans 92,905 111,917 204,822 2,491,998 2,696,820 93,152Other consumer 47,696 30,653 78,349 1,224,930 1,303,279 —Total $3,460,694 $793,324 $4,254,018 $72,038,796 $76,292,814 $93,152(1)Financing receivables include LHFS.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Schedule of Impaired Loans by Class                             | Impaired loans disaggregated by class of financing receivables are summarized as follows:  September 30, 2015  Recorded Investment(1) UnpaidPrincipalBalance RelatedSpecificReserves AverageRecordedInvestment  (in thousands)With no related allowance recorded:        Commercial:        Commercial real estate:        Corporate banking $40,866 $43,717 $— $39,301Middle market commercial real estate 79,320 124,268 — 103,556Santander real estate capital 2,860 2,860 — 2,921Commercial and industrial 2,721 4,144 — 4,374Multi-family 4,834 5,864 — 13,663Other commercial 2,604 2,622 — 1,346Consumer:        Residential mortgages 20,040 20,040 — 21,724Home equity loans and lines of credit 22,999 22,999 — 25,115Retail installment contracts and auto loans 100,835 125,670 — 124,591Personal unsecured loans(2) 14,635 14,635 — 7,614Other consumer 6,013 6,013 — 5,807With an allowance recorded:        Commercial:        Commercial real estate:        Corporate banking 33,744 42,396 10,664 46,847Middle market commercial real estate 36,936 42,635 10,656 48,517Santander real estate capital — — — 1,939Commercial and industrial 80,472 89,708 34,555 73,329Multi-family 5,762 5,767 463 5,871Other commercial 2,429 2,527 449 2,181Consumer:        Residential mortgages 139,279 164,278 28,812 135,046Home equity loans and lines of credit 62,328 73,254 4,832 61,230Retail installment contracts and auto loans 3,393,315 3,734,191 317,655 2,599,160  Personal unsecured loans 1,660 1,950 496 9,068  Other consumer 15,877 20,639 3,720 16,086Total:        Commercial $292,548 $366,508 $56,787 $343,845Consumer 3,776,981 4,183,669 355,515 3,005,441Total $4,069,529 $4,550,177 $412,302 $3,349,286(1)Recorded investment includes deferred loan fees, net of deferred origination costs and unamortized purchase premiums, net of discounts as well as purchase accounting adjustments.(2)Includes LHFS.  December 31, 2014  Recorded Investment(1) UnpaidPrincipalBalance RelatedSpecificReserves AverageRecordedInvestment  (in thousands)With no related allowance recorded:        Commercial:        Commercial real estate:         Corporate banking $37,735 $40,453 $— $40,610 Middle market commercial real estate 127,792 172,766 — 114,465 Santander real estate capital 2,982 2,982 — 1,867Commercial and industrial 6,027 15,580 — 9,580Multi-family 22,492 22,492 — 24,762Other commercial 88 88 — 44Consumer:        Residential mortgages 23,408 23,408 — 57,776Home equity loans and lines of credit 27,230 27,230 — 29,152Retail installment contracts and auto loans 148,347 189,663 — 74,173Personal unsecured loans 592 592 — 296Other consumer 5,600 5,600 — 6,973With an allowance recorded:        Commercial:         Corporate banking 59,950 66,328 25,322 56,856 Middle market commercial real estate 60,098 66,024 17,004 89,472 Santander real estate capital 3,878 6,356 364 6,630Commercial and industrial 66,186 74,737 36,115 83,205Multi-family 5,979 7,076 1,475 8,699Other commercial 1,932 1,995 688 1,055Consumer:        Residential mortgages 130,813 156,669 23,628 339,071Home equity loans and lines of credit 60,132 69,374 5,002 57,516Retail installment contracts and auto loans 1,805,006 2,031,134 192,325 902,504Personal unsecured loans 16,476 16,815 6,508 9,506Other consumer 16,295 22,812 3,264 16,889Total:        Commercial $395,139 $476,877 $80,968 $437,245Consumer 2,233,899 2,543,297 230,727 1,493,856Total $2,629,038 $3,020,174 $311,695 $1,931,101(1)Recorded investment includes deferred loan fees, net of deferred origination costs and unamortized purchase premiums, net of discounts as well as purchase accounting adjustments.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Schedule of Financing Receivable by LTV                         | Residential mortgage and home equity financing receivables by CLTV range are summarized as follows:  Residential MortgagesSeptember 30, 2015 N/A LTV<=70% 70.01-80% 80.01-90% 90.01-100% 100.01-110% LTV>110% Grand Total  (dollars in thousands)N/A $511,932 $12,469 $1,911 $— $— $— $— $526,312<600 133 235,909 74,340 32,482 17,798 10,463 9,814 380,939600-639 1 163,673 47,512 24,478 16,017 5,629 8,704 266,014640-679 237 259,330 84,767 35,774 29,088 10,259 13,600 433,055680-719 21 487,624 183,363 65,314 45,454 11,277 27,042 820,095720-759 344 711,855 322,421 76,584 52,347 12,440 22,610 1,198,601>=760 87 2,109,059 725,490 120,411 61,042 22,409 25,414 3,063,912Grand Total $512,755 $3,979,919 $1,439,804 $355,043 $221,746 $72,477 $107,184 $6,688,928  Home Equity Loans and Lines of CreditSeptember 30, 2015 N/A LTV<=70% 70.01-90% 90.01-110% LTV>110% Grand Total  (dollars in thousands)N/A $194,730 $1,388 $909 $62 $— $197,089<600 11,964 149,242 80,251 25,356 23,108 289,921600-639 9,447 140,744 81,919 20,422 18,578 271,110640-679 11,194 246,235 173,486 35,345 26,511 492,771680-719 13,692 430,783 323,493 54,890 31,492 854,350720-759 13,473 606,189 436,434 75,449 46,248 1,177,793>=760 29,329 1,603,426 1,018,991 142,533 77,905 2,872,184Grand Total $283,829 $3,178,007 $2,115,483 $354,057 $223,842 $6,155,218  Residential MortgagesDecember 31, 2014 N/A LTV<=70% 70.01-80% 80.01-90% 90.01-100% 100.01-110% LTV>110% Grand Total  (dollars in thousands)N/A $437,215 $14,801 $643 $8,676 $14,934 $— $— $476,269<600 94 279,197 91,037 41,341 17,271 15,017 16,327 460,284600-639 200 154,557 50,238 25,861 13,218 6,337 13,446 263,857640-679 — 303,319 87,055 40,863 26,618 11,456 19,530 488,841680-719 25 528,979 161,023 66,898 40,456 11,503 34,473 843,357720-759 314 758,315 271,983 80,077 42,872 16,344 39,927 1,209,832>=760 124 2,328,907 633,004 132,640 60,434 29,738 42,022 3,226,869Grand Total $437,972 $4,368,075 $1,294,983 $396,356 $215,803 $90,395 $165,725 $6,969,309NOTE 5. LOANS AND ALLOWANCE FOR CREDIT LOSSES (continued)  Home Equity Loans and Lines of CreditDecember 31, 2014 N/A LTV<=70% 70.01-90% 90.01-110% LTV>110% Grand Total  (dollars in thousands)N/A $213,289 $2,265 $863 $336 $148 $216,901<600 13,543 158,712 69,381 24,069 20,989 286,694600-639 9,748 154,887 76,431 23,410 14,118 278,594640-679 14,717 279,397 157,214 38,057 25,117 514,502680-719 15,984 488,982 272,083 56,560 33,714 867,323720-759 15,643 672,971 381,828 64,993 45,810 1,181,245>=760 36,962 1,736,574 885,774 125,773 76,638 2,861,721Grand Total $319,886 $3,493,788 $1,843,574 $333,198 $216,534 $6,206,980                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Summary of Performing and Non-performing TDRs                   | The following table summarizes the Company’s performing and non-performing TDRs at the dates indicated: September 30, 2015 December 31, 2014 (in thousands)Performing$3,434,409 $2,117,789Non-performing523,250 377,239Total$3,957,659 $2,495,028                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      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| Schedule of Troubled Debt Restructurings                        | The following tables detail the activity of TDRs for the three-month and nine-month periods endedSeptember 30, 2015 and September 30, 2014, respectively:  Three-Month Period Ended September 30, 2015 Number ofContracts Pre-ModificationOutstanding RecordedInvestment(1) Post-ModificationOutstanding RecordedInvestment(2) (dollars in thousands)Commercial: Commercial real estate:      Corporate Banking— $— $—Commercial and industrial205 7,034 7,005Consumer:     Residential mortgages(3)25 3,758 4,028 Home equity loans and lines of credit31 2,581 2,992 Retail installment contracts and auto loans  46,034 829,574 823,967 Personal unsecured loans4,058 4,894 4,870 Other consumer3 310 328Total50,356 $848,151 $843,190       Nine-Month Period Ended September 30, 2015 Number ofContracts Pre-ModificationOutstanding RecordedInvestment(1) Post-ModificationOutstanding RecordedInvestment(2) (dollars in thousands)Commercial:     Commercial real estate:      Corporate Banking16 $28,418 $24,546 Middle market commercial real estate1 14,439 14,439Commercial and industrial417 13,694 13,652Consumer:     Residential mortgages(3)114 17,929 18,765 Home equity loans and lines of credit92 7,274 8,281 Retail installment contracts and auto loans  201,970 3,071,671 3,059,425 Personal unsecured loans13,217 15,774 15,685 Other consumer20 1,441 1,484Total215,847 $3,170,640 $3,156,277(1)Pre-modification outstanding recorded investment amount is the month-end balance prior to the month the modification occurred.(2)Post-modification outstanding recorded investment amount is the month-end balance for the month that the modification occurred.(3)The post-modification outstanding recorded investment amounts for residential mortgages exclude interest reserves. NOTE 5. LOANS AND ALLOWANCE FOR CREDIT LOSSES (continued) Three-Month Period Ended September 30, 2014 Number of Contracts Pre-ModificationOutstanding RecordedInvestment(1) Post-ModificationOutstanding RecordedInvestment(2) (dollars in thousands)Commercial:     Commercial real estate:     Corporate banking2 $16,739 $16,615Middle markets commercial real estate2 19,024 19,024Other commercial2 1,456 1,445Consumer:     Residential mortgages(3)65 13,096 13,444Home equity loans and lines of credit32 2,813 2,813Retail installment contracts and auto loans (4)43,602 608,408 559,565Personal unsecured loans(6)5,653 6,284 6,311Other consumer2 124 124Total49,360 $667,944 $619,341             Nine-Month Period Ended September 30, 2014 Number of Contracts Pre-ModificationOutstanding RecordedInvestment(1) Post-ModificationOutstanding RecordedInvestment(2) (dollars in thousands)Commercial:     Commercial real estate:     Corporate banking23 $70,017 $68,656Middle markets commercial real estate5 28,963 25,851Other commercial5 2,503 2,472Consumer:     Residential mortgages222 41,830 42,510Home equity loans and lines of credit86 7,991 7,991Retail installment contracts and auto loans(5)78,216 1,027,275 900,642Personal unsecured loans(6)10,542 11,618 11,457Other consumer7 536 537Total89,106 $1,190,733 $1,060,116(1)Pre-modification outstanding recorded investment amount is the month-end balance prior to the month the modification occurred. (2)Post-modification outstanding recorded investment amount is the month-end balance for the month that the modification occurred.(3)The post-modification outstanding recorded investment amounts for residential mortgages exclude interest reserves. (4)The number of RICs that were modified decreased by 15,853 contracts with a corresponding decrease of $384.8 million to the pre-modification outstanding recorded investment and a decrease of $367.5 million to the post-modification outstanding recorded investment to correct the TDR activity that occurred during the three-month period ended September 30, 2014.  (5)The number of RICs that were modified decreased by 50,012 contracts with a corresponding decrease of $1.0 billion to the pre-modification outstanding recorded investment and a decrease of $1.0 billion to the post-modification outstanding recorded investment to correct the TDR activity that occurred during the nine-month period ended September 30, 2014.  (6)The number of Personal unsecured loans that were modified decreased by 8,839 and 28,197 contracts with a corresponding decrease of $5.1 million and $14.6 million to the Pre-modification outstanding recorded investment and a decrease of $5.0 million and $14.6 million to the post-modification outstanding recorded investment to correct the TDR activity that occurred during the three and nine-month periods ended September 30, 2014, respectively.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Schedule of Troubled Debt Restructurings Subsequently Defaulted | The following table details TDRs that became TDRs during the past twelve-month period and have subsequently defaulted during the three-month and nine-month periods endedSeptember 30, 2015 and September 30, 2014, respectively. Three-Month PeriodEnded September 30,  Nine-Month PeriodEnded September 30, 2015 2014 2015 2014 Number ofContracts Recorded Investment(1) Number ofContracts Recorded Investment(1) Number ofContracts Recorded Investment(1) Number ofContracts Recorded Investment(1) (dollars in thousands)Commercial               Commercial and industrial8 $134 — $— 25 $652 — $—Consumer:               Residential mortgages2 486 1 298 15 2,307 22 2,993Home equity loans and lines of credit 3 728 1 65 14 1,665 3 377Retail installment contracts and auto loans(2)991 60,959 2,981 17,811 28,923 357,914 3,760 24,240Unsecured loans(3)871 1,011 820 861 3,422 3,681 1,090 1,166Other consumer— — — — 2 244 — —Total1,875 $63,318 3,803 $19,035 32,401 $366,463 4,875 $28,776(1)The recorded investment represents the period-end balance at September 30, 2015 and 2014. Does not include Chapter 7 bankruptcy TDRs.(2)The number of RIC TDRs that subsequently defaulted increased by 2,595 and 2,586 contracts, respectively, with an associated increase in the recorded investment of $10.6 million and $7.7 million, respectively, to correct the subsequently defaulted TDR activity for the three-month and nine-month periods ended September 30, 2014.(3)The number of Unsecured loan contract TDRs that subsequently defaulted increased by 820 and 1,089 contracts, respectively, with an associated increase in the recorded investment of $0.9 million  and $1.1 million, respectively, to correct the subsequently defaulted TDR activity for the three and nine-month periods ended September 30, 2014.                                                                                                                                                                                                                                                                                            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| Commercial                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          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| **Financing Receivable, Recorded Investment [Line Items]**      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            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| Schedule of Loans by Credit Quality Indicators                  | The following table reconciles the Company's recorded investment classified by its major loan classifications to its commercial loan classifications utilized in its determination of the allowance for loan losses and other credit quality disclosures at September 30, 2015 and December 31, 2014, respectively:Commercial Portfolio Segment(2)    Major Loan Classifications(1) September 30, 2015 December 31, 2014  (in thousands)Commercial loans held for investment:    Commercial real estate:    Corporate Banking $2,967,780 $3,218,151Middle Markets Real Estate 3,965,173 3,743,100Santander Real Estate Capital 1,562,229 1,777,982Total commercial real estate 8,495,182 8,739,233Commercial and industrial loans (3) 19,361,751 17,092,312Multi-family loans 9,600,527 8,705,890Other commercial 2,366,742 2,084,232Total commercial loans held for investment $39,824,202 $36,621,667 (1)These represent the Company's loan categories based on the SEC's Regulation S-X, Article 9. (2)These represent the Company's loan classes used to determine its allowance for loan and lease losses in accordance with ASC 310-10.(3)Excludes zero and $19.1 million of Commercial and Industrial LHFS at September 30, 2015 and December 31, 2014, respectively.Commercial loan credit quality indicators by class of financing receivables are summarized as follows:  Commercial Real Estate        September 30, 2015 Corporatebanking Middlemarketcommercialreal estate Santanderreal estatecapital Commercial and industrial Multi-family Remainingcommercial Total(1)  (in thousands)Regulatory Rating:              Pass $2,623,982 $3,765,920 $1,392,754 $18,527,810 $9,333,083 $2,320,236 $37,963,785Special Mention 118,536 48,842 121,441 374,448 195,710 29,950 888,927Substandard 215,912 127,213 47,375 429,623 71,301 16,251 907,675Doubtful 9,350 23,198 659 29,870 433 305 63,815Total commercial loans $2,967,780 $3,965,173 $1,562,229 $19,361,751 $9,600,527 $2,366,742 $39,824,202(1)Financing receivables include LHFS.  Commercial Real Estate        December 31, 2014 Corporatebanking Middlemarketcommercialreal estate Santanderreal estatecapital Commercial and industrial Multi-family Remainingcommercial Total(1)  (in thousands)Regulatory Rating:              Pass $2,910,957 $3,472,448 $1,564,983 $16,495,319 $8,533,427 $2,064,947 $35,042,081Special Mention 83,122 61,166 133,950 237,331 131,677 8,475 655,721Substandard 192,911 174,882 76,232 358,782 40,355 10,311 853,473Doubtful 31,161 34,604 2,817 19,974 431 499 89,486Total commercial loans $3,218,151 $3,743,100 $1,777,982 $17,111,406 $8,705,890 $2,084,232 $36,640,761(1)Financing receivables include LHFS.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Consumer                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   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| **Financing Receivable, Recorded Investment [Line Items]**      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   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| Schedule of Loans by Credit Quality Indicators                  | Consumer Portfolio Segment(2)    Major Loan Classifications(1) September 30, 2015 December 31, 2014  (in thousands)Consumer loans secured by real estate:   Residential mortgages(3) $6,408,164 $6,773,575Home equity loans and lines of credit 6,155,218 6,206,980Total consumer loans secured by real estate 12,563,382 12,980,555Consumer loans not secured by real estate:   Retail installment contracts and auto loans(4) 24,597,860 22,430,241Personal unsecured loans(5) 644,548 2,696,820Other consumer 1,079,729 1,303,279Total consumer loans held for investment $38,885,519 $39,410,895 (1)These represent the Company's loan categories based on the SEC's Regulation S-X, Article 9.(2)These represent the Company's loan classes used to determine its allowance for loan and lease losses in accordance with ASC 310-10.(3)Home mortgages exclude $280.8 million and $195.7 million of LHFS at September 30, 2015 and December 31, 2014, respectively.(4)Retail installment contracts and auto loans exclude $825.8 million and $45.4 million of LHFS at September 30, 2015 and December 31, 2014, respectively.(5)Personal unsecured loans exclude $1.9 billion of LHFS at September 30, 2015. There were no personal unsecured loans HFS at December 31, 2014.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             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Schedule of Financing Receivable by Credit Score and by LTV [Table Text Block]
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Tabular disclosure of financing receivables (examples of financing receivables include loans, trade accounts receivable and notes receivable) and activity in the allowance for credit losses account.
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Tabular disclosure of financing receivables by credit quality indicator. The credit quality indicator is a statistic about the credit quality of financing receivables. Examples include, but not limited to, consumer credit risk scores, credit-rating-agency ratings, an entity's internal credit risk grades, loan-to-value ratios, collateral, collection experience and other internal metrics.
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
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Tabular disclosure of impaired financing receivables.
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Tabular disclosure of financing receivables that are past due but not impaired, financing receivables that are 90 days past due and still accruing, and financing receivables on nonaccrual status.
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Tabular disclosure of the various types of trade accounts and notes receivable and for each the gross carrying value, allowance, and net carrying value as of the balance sheet date. Presentation is categorized by current, noncurrent and unclassified receivables.
+ References
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| - Definition
Tabular disclosure of nonaccrual and past due financing receivables (such as loans and trade receivables), including: (a) the recorded investment in loans and trade receivables, if applicable, on nonaccrual status as of each balance sheet date (b) the recorded investment in loans and trade receivables, if applicable, past due 90 days or more and still accruing.
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| - Definition
Tabular disclosure of financing receivables and troubled debt restructurings.
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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953676-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953682-111524
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