| **INVESTMENT SECURITIES (Available-for-sale Securities) (Details) - USD ($) $ in Thousands** | 3 Months Ended | 9 Months Ended |          |
|----------------------------------------------------------------------------------------------|----------------|----------------|----------|
||
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | $ 21,028,749   |           |     | $ 21,028,749 |   | $ 15,992,659 |
| Gross Unrealized Gains                                                                       | 145,680        |           |     | 145,680 |   | 100,798 |
| Gross Unrealized Loss                                                                        | (123,245)      |           |     | (123,245) |   | (185,379) |
| Fair Value                                                                                   | 21,051,184     |           |     | 21,051,184 |   | 15,908,078 |
| Proceeds from the sales of available-for-sale securities                                     | 497,182        |           | $ 21,138 | 2,751,790 | $ 311,019 |   |
| FHLMC | Mortgage banking income                                                              |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Gain on sale of mortgage-backed debt securities                                              |           | $ 9,800        |     |   |   |   |
| US Treasury securities                                                                       |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 3,191,564      |           |     | 3,191,564 |   | 1,692,838 |
| Gross Unrealized Gains                                                                       | 18,299         |           |     | 18,299 |   | 2,985 |
| Gross Unrealized Loss                                                                        | 0              |           |     | 0 |   | (56) |
| Fair Value                                                                                   | 3,209,863      |           |     | 3,209,863 |   | 1,695,767 |
| Corporate debt securities                                                                    |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 1,554,216      |           |     | 1,554,216 |   | 2,159,681 |
| Gross Unrealized Gains                                                                       | 17,224         |           |     | 17,224 |   | 29,630 |
| Gross Unrealized Loss                                                                        | (8,341)        |           |     | (8,341) |   | (6,910) |
| Fair Value                                                                                   | 1,563,099      |           |     | 1,563,099 |   | 2,182,401 |
| Asset-backed securities (ABS)                                                                |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 1,938,581      |           |     | 1,938,581 |   | 2,707,207 |
| Gross Unrealized Gains                                                                       | 7,111          |           |     | 7,111 |   | 17,787 |
| Gross Unrealized Loss                                                                        | (1,041)        |           |     | (1,041) |   | (4,591) |
| Fair Value                                                                                   | 1,944,651      |           |     | 1,944,651 |   | 2,720,403 |
| Equity securities                                                                            |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 10,826         |           |     | 10,826 |   | 10,619 |
| Gross Unrealized Gains                                                                       | 3              |           |     | 3 |   | 3 |
| Gross Unrealized Loss                                                                        | (301)          |           |     | (301) |   | (279) |
| Fair Value                                                                                   | 10,528         |           |     | 10,528 |   | 10,343 |
| State and municipal securities                                                               |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 750,946        |           |     | 750,946 |   | 1,790,776 |
| Gross Unrealized Gains                                                                       | 12,524         |           |     | 12,524 |   | 35,071 |
| Gross Unrealized Loss                                                                        | (2,148)        |           |     | (2,148) |   | (2,385) |
| Fair Value                                                                                   | 761,322        |           |     | 761,322 |   | 1,823,462 |
| U.S. government agencies - Residential                                                       |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 4,077,361      |           |     | 4,077,361 |   | 2,151,111 |
| Gross Unrealized Gains                                                                       | 31,836         |           |     | 31,836 |   | 1,626 |
| Gross Unrealized Loss                                                                        | (16,724)       |           |     | (16,724) |   | (33,811) |
| Fair Value                                                                                   | 4,092,473      |           |     | 4,092,473 |   | 2,118,926 |
| U.S. government agencies - Commercial                                                        |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 986,989        |           |     | 986,989 |   | 472,611 |
| Gross Unrealized Gains                                                                       | 10,283         |           |     | 10,283 |   | 183 |
| Gross Unrealized Loss                                                                        | (5,109)        |           |     | (5,109) |   | (7,186) |
| Fair Value                                                                                   | 992,163        |           |     | 992,163 |   | 465,608 |
| FHLMC and FNMA - Residential debt securities                                                 |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 8,379,831      |           |     | 8,379,831 |   | 4,971,045 |
| Gross Unrealized Gains                                                                       | 46,998         |           |     | 46,998 |   | 12,817 |
| Gross Unrealized Loss                                                                        | (89,154)       |           |     | (89,154) |   | (129,990) |
| Fair Value                                                                                   | 8,337,675      |           |     | 8,337,675 |   | 4,853,872 |
| FHLMC and FNMA - Residential debt securities | FHLMC                                         |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| MBS issued by the FHLMC                                                                      |           | 243,900        |     |   |   |   |
| FHLMC and FNMA - Commercial debt securities                                                  |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 138,383        |           |     | 138,383 |   | 23,929 |
| Gross Unrealized Gains                                                                       | 1,402          |           |     | 1,402 |   | 157 |
| Gross Unrealized Loss                                                                        | (427)          |           |     | (427) |   | (171) |
| Fair Value                                                                                   | 139,358        |           |     | 139,358 |   | 23,915 |
| Non-agency securities                                                                        |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Amortized Cost                                                                               | 52             |           |     | 52 |   | 12,842 |
| Gross Unrealized Gains                                                                       | 0              |           |     | 0 |   | 539 |
| Gross Unrealized Loss                                                                        | 0              |           |     | 0 |   | 0 |
| Fair Value                                                                                   | $ 52           |           |     | $ 52 |   | $ 13,381 |
| Residential mortgages | FHLMC                                                                |           |           |     |   |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |           |           |     |   |   |   |
| Proceeds from the sales of available-for-sale securities                                     |           | $ 234,500      |     |   |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Net gain (loss) resulting from the sales of securitized, pay-through debt securities collateralized by real estate mortgage loans (mortgages).
+ 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 210.9-04.13(h)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as available-for-sale.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Mortgage-Backed Securities -URI http://asc.fasb.org/extlink&oid=6517959
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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.
+ References
No definition available.
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