| **INVESTMENT SECURITIES (Available-for-sale Securities) (Details) - USD ($) $ in Thousands** | 12 Months Ended |
|----------------------------------------------------------------------------------------------|-----------------|
||
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | $ 21,006,066    | $ 15,992,659 |   |
| Gross Unrealized Gains                                                                       | 63,973          | 100,798 |   |
| Gross Unrealized Loss                                                                        | (218,544)       | (185,379) |   |
| Fair Value                                                                                   | 20,851,495      | 15,908,078 |   |
| Proceeds from the sales of available-for-sale securities                                     | 2,809,779       | 341,513 | $ 8,050,028 |
| Accrued investment income receivable                                                         | 65,100          | 67,300 |   |
| FHLMC | Mortgage banking income                                                              |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Gain on sale of mortgage-backed debt securities                                              | 22,000          | 49,800 |   |
| U.S. Treasury securities                                                                     |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 3,192,411       | 1,692,838 |   |
| Gross Unrealized Gains                                                                       | 1,658           | 2,985 |   |
| Gross Unrealized Loss                                                                        | (5,681)         | (56) |   |
| Fair Value                                                                                   | 3,188,388       | 1,695,767 |   |
| Corporate debt securities                                                                    |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 1,476,801       | 2,159,681 |   |
| Gross Unrealized Gains                                                                       | 10,021          | 29,630 |   |
| Gross Unrealized Loss                                                                        | (11,248)        | (6,910) |   |
| Fair Value                                                                                   | 1,475,574       | 2,182,401 |   |
| Asset-backed securities (ABS)                                                                |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 1,763,178       | 2,707,207 |   |
| Gross Unrealized Gains                                                                       | 7,826           | 17,787 |   |
| Gross Unrealized Loss                                                                        | (1,494)         | (4,591) |   |
| Fair Value                                                                                   | 1,769,510       | 2,720,403 |   |
| Equity securities                                                                            |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 10,894          | 10,619 |   |
| Gross Unrealized Gains                                                                       | 1               | 3 |   |
| Gross Unrealized Loss                                                                        | (408)           | (279) |   |
| Fair Value                                                                                   | 10,487          | 10,343 |   |
| State and municipal securities                                                               |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 748,696         | 1,790,776 |   |
| Gross Unrealized Gains                                                                       | 19,616          | 35,071 |   |
| Gross Unrealized Loss                                                                        | (432)           | (2,385) |   |
| Fair Value                                                                                   | 767,880         | 1,823,462 |   |
| U.S. government agencies - Residential                                                       |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 4,033,041       | 2,151,111 |   |
| Gross Unrealized Gains                                                                       | 10,225          | 1,626 |   |
| Gross Unrealized Loss                                                                        | (36,513)        | (33,811) |   |
| Fair Value                                                                                   | 4,006,753       | 2,118,926 |   |
| U.S. government agencies - Commercial                                                        |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 1,006,161       | 472,611 |   |
| Gross Unrealized Gains                                                                       | 3,347           | 183 |   |
| Gross Unrealized Loss                                                                        | (7,153)         | (7,186) |   |
| Fair Value                                                                                   | 1,002,355       | 465,608 |   |
| FHLMC and FNMA - Residential debt securities                                                 |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 8,636,745       | 4,971,045 |   |
| Gross Unrealized Gains                                                                       | 10,556          | 12,817 |   |
| Gross Unrealized Loss                                                                        | (153,128)       | (129,990) |   |
| Fair Value                                                                                   | 8,494,173       | 4,853,872 |   |
| FHLMC and FNMA - Residential debt securities | FHLMC                                         |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| MBS issued by the FHLMC                                                                      | 416,700         | 2,100,000 |   |
| FHLMC and FNMA - Commercial debt securities                                                  |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 138,094         | 23,929 |   |
| Gross Unrealized Gains                                                                       | 723             | 157 |   |
| Gross Unrealized Loss                                                                        | (2,487)         | (171) |   |
| Fair Value                                                                                   | 136,330         | 23,915 |   |
| Non-agency securities                                                                        |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Amortized Cost                                                                               | 45              | 12,842 |   |
| Gross Unrealized Gains                                                                       | 0               | 539 |   |
| Gross Unrealized Loss                                                                        | 0               | 0 |   |
| Fair Value                                                                                   | 45              | 13,381 |   |
| Residential mortgages | FHLMC                                                                |            |   |   |
| **Schedule of Available-for-sale Securities [Line Items]**                                   |            |   |   |
| Proceeds from the sales of available-for-sale securities                                     | $ 395,200       | $ 2,100,000 |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Interest, dividends, rents, ancillary and other revenues earned but not yet received by the entity on its investments.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.
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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.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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.
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| - 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.
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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).
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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.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.
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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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No definition available.
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