| **LOANS AND ALLOWANCE FOR CREDIT LOSSES (As Restated) (Rollforward of Allowance for Credit Losses) (Details) - USD ($) $ in Thousands** | 3 Months Ended | 12 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------------------------|----------------|-----------------|
||
| **Allowance for Loan Losses [Roll Forward]**                                                                                            |           |            |   |   |
| Allowance for loan and lease losses, beginning of period                                                                                | $ 1,701,602    | $ 1,701,602     | $ 834,337 | $ 1,013,469 |
| Provision for loan and lease losses                                                                                                     |           | 3,998,200       | 2,495,243 | 36,850 |
| Other                                                                                                                                   |           | (27,117)        | (61,220) |   |
| Charge-offs                                                                                                                             |           | (4,600,256)     | (2,774,465) | (315,204) |
| Recoveries                                                                                                                              |           | 2,088,282       | 1,207,707 | 99,222 |
| Charge-offs, net of recoveries                                                                                                          |           | (2,511,974)     | (1,566,758) | (215,982) |
| Allowance for loan and lease losses, end of period                                                                                      |           | 3,160,711       | 1,701,602 | 834,337 |
| Reserve for unfunded lending commitments, beginning of period                                                                           | 132,641        | 132,641         | 220,000 | 210,000 |
| Provision for unfunded lending commitments                                                                                              |           | 14,756          | (82,000) | 10,000 |
| Loss on unfunded lending commitments                                                                                                    |           | 0               | (5,359) |   |
| Reserve for unfunded lending commitments, end of period                                                                                 |           | 147,397         | 132,641 | 220,000 |
| Total allowance for credit losses, end of period                                                                                        |           | 3,308,108       | 1,834,243 | 1,054,337 |
| Ending balance, individually evaluated for impairment                                                                                   |           | 944,091         | 136,100 | 225,796 |
| Ending balance, collectively evaluated for impairment                                                                                   |           | 2,216,620       | 1,565,502 | 608,541 |
| **Financing receivables:**                                                                                                              |           |            |   |   |
| Ending balance                                                                                                                          |           | 82,557,074      | 76,255,719 | 50,050,626 |
| Ending balance, evaluated under the fair value option or lower of cost or fair value                                                    |           | 3,511,937       | 1,106,163 | 128,949 |
| Ending balance, individually evaluated for impairment                                                                                   |           | 4,607,310       | 2,618,749 | 1,233,152 |
| Ending balance, collectively evaluated for impairment                                                                                   |           | 74,437,827      | 72,530,807 | 48,688,525 |
| Sale of TDRs and NPLs classified as held-for-sale                                                                                       | 1,000,000      |            | 484,200 |   |
| Commercial                                                                                                                              |           |            |   |   |
| **Allowance for Loan Losses [Roll Forward]**                                                                                            |           |            |   |   |
| Allowance for loan and lease losses, beginning of period                                                                                | 401,553        | 401,553         | 443,074 | 580,931 |
| Provision for loan and lease losses                                                                                                     |           | 138,482         | 27,818 | (67,472) |
| Other                                                                                                                                   |           | 0               |   |   |
| Charge-offs                                                                                                                             |           | (165,682)       | (109,718) | (123,517) |
| Recoveries                                                                                                                              |           | 61,364          | 40,379 | 53,132 |
| Charge-offs, net of recoveries                                                                                                          |           | (104,318)       | (69,339) | (70,385) |
| Allowance for loan and lease losses, end of period                                                                                      |           | 435,717         | 401,553 | 443,074 |
| Reserve for unfunded lending commitments, beginning of period                                                                           | 132,641        | 132,641         | 220,000 | 210,000 |
| Provision for unfunded lending commitments                                                                                              |           | 14,756          | (82,000) | 10,000 |
| Loss on unfunded lending commitments                                                                                                    |           | 0               | (5,359) |   |
| Reserve for unfunded lending commitments, end of period                                                                                 |           | 147,397         | 132,641 | 220,000 |
| Total allowance for credit losses, end of period                                                                                        |           | 583,114         | 534,194 | 663,074 |
| Ending balance, individually evaluated for impairment                                                                                   |           | 48,511          | 80,701 | 90,594 |
| Ending balance, collectively evaluated for impairment                                                                                   |           | 387,206         | 320,852 | 352,480 |
| **Financing receivables:**                                                                                                              |           |            |   |   |
| Ending balance                                                                                                                          |           | 40,712,120      | 36,641,277 | 32,169,154 |
| Ending balance, evaluated under the fair value option or lower of cost or fair value                                                    |           | 86,399          | 19,094 | 17,932 |
| Ending balance, individually evaluated for impairment                                                                                   |           | 403,653         | 494,565 | 479,343 |
| Ending balance, collectively evaluated for impairment                                                                                   |           | 40,222,068      | 36,127,618 | 31,671,879 |
| Consumer                                                                                                                                |           |            |   |   |
| **Allowance for Loan Losses [Roll Forward]**                                                                                            |           |            |   |   |
| Allowance for loan and lease losses, beginning of period                                                                                | 1,267,025      | 1,267,025       | 363,647 | 407,259 |
| Provision for loan and lease losses                                                                                                     |           | 3,847,414       | 2,462,017 | 101,985 |
| Other                                                                                                                                   |           | (27,117)        | (61,220) |   |
| Charge-offs                                                                                                                             |           | (4,434,574)     | (2,664,747) | (191,687) |
| Recoveries                                                                                                                              |           | 2,026,918       | 1,167,328 | 46,090 |
| Charge-offs, net of recoveries                                                                                                          |           | (2,407,656)     | (1,497,419) | (145,597) |
| Allowance for loan and lease losses, end of period                                                                                      |           | 2,679,666       | 1,267,025 | 363,647 |
| Reserve for unfunded lending commitments, beginning of period                                                                           | 0              | 0               | 0 | 0 |
| Provision for unfunded lending commitments                                                                                              |           | 0               | 0 | 0 |
| Loss on unfunded lending commitments                                                                                                    |           | 0               | 0 |   |
| Reserve for unfunded lending commitments, end of period                                                                                 |           | 0               | 0 | 0 |
| Total allowance for credit losses, end of period                                                                                        |           | 2,679,666       | 1,267,025 | 363,647 |
| Ending balance, individually evaluated for impairment                                                                                   |           | 895,580         | 55,399 | 135,202 |
| Ending balance, collectively evaluated for impairment                                                                                   |           | 1,784,086       | 1,211,626 | 228,445 |
| **Financing receivables:**                                                                                                              |           |            |   |   |
| Ending balance                                                                                                                          |           | 41,844,954      | 39,614,442 | 17,881,472 |
| Ending balance, evaluated under the fair value option or lower of cost or fair value                                                    |           | 3,425,538       | 1,087,069 | 111,017 |
| Ending balance, individually evaluated for impairment                                                                                   |           | 4,203,657       | 2,124,184 | 753,809 |
| Ending balance, collectively evaluated for impairment                                                                                   |           | 34,215,759      | 36,403,189 | 17,016,646 |
| Unallocated                                                                                                                             |           |            |   |   |
| **Allowance for Loan Losses [Roll Forward]**                                                                                            |           |            |   |   |
| Allowance for loan and lease losses, beginning of period                                                                                | 33,024         | 33,024          | 27,616 | 25,279 |
| Provision for loan and lease losses                                                                                                     |           | 12,304          | 5,408 | 2,337 |
| Other                                                                                                                                   |           | 0               |   |   |
| Charge-offs                                                                                                                             |           | 0               | 0 | 0 |
| Recoveries                                                                                                                              |           | 0               | 0 | 0 |
| Charge-offs, net of recoveries                                                                                                          |           | 0               | 0 | 0 |
| Allowance for loan and lease losses, end of period                                                                                      |           | 45,328          | 33,024 | 27,616 |
| Reserve for unfunded lending commitments, beginning of period                                                                           | 0              | 0               | 0 | 0 |
| Provision for unfunded lending commitments                                                                                              |           | 0               | 0 | 0 |
| Loss on unfunded lending commitments                                                                                                    |           | 0               | 0 |   |
| Reserve for unfunded lending commitments, end of period                                                                                 |           | 0               | 0 | 0 |
| Total allowance for credit losses, end of period                                                                                        |           | 45,328          | 33,024 | 27,616 |
| Ending balance, individually evaluated for impairment                                                                                   |           | 0               | 0 | 0 |
| Ending balance, collectively evaluated for impairment                                                                                   |           | 45,328          | 33,024 | 27,616 |
| **Financing receivables:**                                                                                                              |           |            |   |   |
| Ending balance                                                                                                                          |           | 0               | 0 | 0 |
| Ending balance, evaluated under the fair value option or lower of cost or fair value                                                    |           | 0               | 0 | 0 |
| Ending balance, individually evaluated for impairment                                                                                   |           | 0               | 0 | 0 |
| Ending balance, collectively evaluated for impairment                                                                                   |           | 0               | 0 | 0 |
| Retail installment contracts and auto loans, purchased                                                                                  |           |            |   |   |
| **Allowance for Loan Losses [Roll Forward]**                                                                                            |           |            |   |   |
| Allowance for loan and lease losses, beginning of period                                                                                | 963            | 963             | 0 |   |
| Provision for loan and lease losses                                                                                                     |           | 1,106,462       | 799,208 |   |
| Other                                                                                                                                   |           | (27,117)        |   |   |
| Charge-offs                                                                                                                             |           | (1,516,951)     | (1,732,218) |   |
| Recoveries                                                                                                                              |           | 1,027,450       | 933,973 |   |
| Charge-offs, net of recoveries                                                                                                          |           | (489,501)       | (798,245) |   |
| Allowance for loan and lease losses, end of period                                                                                      |           | 590,807         | 963 | 0 |
| Retail installment contracts and auto loans, originated                                                                                 |           |            |   |   |
| **Allowance for Loan Losses [Roll Forward]**                                                                                            |           |            |   |   |
| Allowance for loan and lease losses, beginning of period                                                                                | 709,024        | 709,024         | 0 |   |
| Provision for loan and lease losses                                                                                                     |           | 2,313,825       | 982,506 |   |
| Other                                                                                                                                   |           | 0               |   |   |
| Charge-offs                                                                                                                             |           | (2,035,878)     | (420,500) |   |
| Recoveries                                                                                                                              |           | 905,018         | 147,018 |   |
| Charge-offs, net of recoveries                                                                                                          |           | (1,130,860)     | (273,482) |   |
| Allowance for loan and lease losses, end of period                                                                                      |           | 1,891,989       | 709,024 | 0 |
| Retail installment contracts and auto loans                                                                                             |           |            |   |   |
| **Allowance for Loan Losses [Roll Forward]**                                                                                            |           |            |   |   |
| Allowance for loan and lease losses, beginning of period                                                                                | $ 709,987      | 709,987         | 0 |   |
| Provision for loan and lease losses                                                                                                     |           | 3,420,287       | 1,781,714 |   |
| Other                                                                                                                                   |           | (27,117)        |   |   |
| Charge-offs                                                                                                                             |           | (3,552,829)     | (2,152,718) |   |
| Recoveries                                                                                                                              |           | 1,932,468       | 1,080,991 |   |
| Charge-offs, net of recoveries                                                                                                          |           | (1,620,361)     | (1,071,727) |   |
| Allowance for loan and lease losses, end of period                                                                                      |           | $ 2,482,796     | $ 709,987 | $ 0 |

| X                                                                                                                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
A valuation allowance for financing receivables that are expected to be uncollectible and reserve for unfunded lending commitments.
+ References
No definition available.
+ Details**Name:**sov_FinancingReceivableAllowanceForCreditLossesAndReserveForUnfundedCommitments**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Net amount of direct write-downs and recoveries of financing receivables charged against the allowance.
+ References
No definition available.
+ Details**Name:**sov_FinancingReceivableAllowanceForCreditLossesNetWriteDowns**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Gain (Loss) on Unfunded Commitments
+ References
No definition available.
+ Details**Name:**sov_GainLossonUnfundedCommitments**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Increase (Decrease) in Allowance for Credit Losses from Sale of Troubled Debt Restructuring and Non-performing Loans Held-for-sale
+ References
No definition available.
+ Details**Name:**sov_IncreaseDecreaseinAllowanceforCreditLossesfromSaleofTroubledDebtRestructuringandNonperformingLoansHeldforsale**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Loans Receivable Held-for-sale, Net, Fair Value Option
+ References
No definition available.
+ Details**Name:**sov_LoansReceivableHeldforsaleNetFairValueOption**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Net change in reserve for unfunded commitments which is included in the provision for credit losses.
+ References
No definition available.
+ Details**Name:**sov_NetChangeInReserveForUnfundedCommitments**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Reserve for unfunded loan commitments and letters of credit.
+ References
No definition available.
+ Details**Name:**sov_ReserveForUnfundedCommitments**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of reduction of allowance reserve for credit loss arising from sale of loan and lease portfolios.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878
+ Details**Name:**us-gaap_AllowanceForLoanAndLeaseLossesLoansSold**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
A valuation allowance for financing receivables that are expected to be uncollectible.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524
+ Details**Name:**us-gaap_FinancingReceivableAllowanceForCreditLosses**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524
+ Details**Name:**us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524
+ Details**Name:**us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of recovery of financing receivables doubtful of collection that were previously charged off.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524
+ Details**Name:**us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.
+ References
No definition available.
+ Details**Name:**us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of direct write-downs of financing receivables charged against the allowance.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524
+ Details**Name:**us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The balance of financing receivables that were collectively evaluated for impairment.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524
+ Details**Name:**us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The balance of financing receivables that were individually evaluated for impairment.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524
+ Details**Name:**us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.10(3)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878
+ Details**Name:**us-gaap_NotesReceivableGross**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
+ Details**Name:**us-gaap_NotesReceivableNetAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expense related to estimated loss from loan and lease transactions.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.11) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524
+ Details**Name:**us-gaap_ProvisionForLoanAndLeaseLosses**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_UnallocatedFinancingReceivablesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=sov_RetailInstallmentContractsandAutoLoansPurchasedMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=sov_RetailInstallmentContractsandAutoLoansOriginatedMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=sov_RetailInstallmentContractsandAutoLoansMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |