| **INVESTMENT SECURITIES (Contractual Maturity of Debt Securities) (Details) - USD ($) $ in Thousands** | 12 Months Ended |
|--------------------------------------------------------------------------------------------------------|-----------------|
||
| **Amortized Cost**                                                                                     |            |   |   |
| Federal income tax at statutory rate                                                                   | 35.00%          | 35.00% | 35.00% |
| U.S Treasury securities                                                                                |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 500,550       |   |   |
| Due after 1 year but within 5 years                                                                    | 2,687,838       |   |   |
| Due after 5 years but within 10 years                                                                  | 0               |   |   |
| Due After 10 Years/No Maturity                                                                         | 0               |   |   |
| Total                                                                                                  | $ 3,188,388     |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Total                                                                                                  | 0.97%           |   |   |
| Corporate debt securities                                                                              |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 65,465        |   |   |
| Due after 1 year but within 5 years                                                                    | 1,410,109       |   |   |
| Due after 5 years but within 10 years                                                                  | 0               |   |   |
| Due After 10 Years/No Maturity                                                                         | 0               |   |   |
| Total                                                                                                  | $ 1,475,574     |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Total                                                                                                  | 2.28%           |   |   |
| Asset-backed securities                                                                                |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 203,802       |   |   |
| Due after 1 year but within 5 years                                                                    | 1,354,216       |   |   |
| Due after 5 years but within 10 years                                                                  | 39,949          |   |   |
| Due After 10 Years/No Maturity                                                                         | 171,543         |   |   |
| Total                                                                                                  | $ 1,769,510     |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Total                                                                                                  | 1.41%           |   |   |
| State and municipal securities                                                                         |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 0             |   |   |
| Due after 1 year but within 5 years                                                                    | 5               |   |   |
| Due after 5 years but within 10 years                                                                  | 190,926         |   |   |
| Due After 10 Years/No Maturity                                                                         | 576,949         |   |   |
| Total                                                                                                  | $ 767,880       |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Total                                                                                                  | 2.74%           |   |   |
| U.S. government agencies - Residential                                                                 |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 0             |   |   |
| Due after 1 year but within 5 years                                                                    | 6,308           |   |   |
| Due after 5 years but within 10 years                                                                  | 213             |   |   |
| Due After 10 Years/No Maturity                                                                         | 4,000,232       |   |   |
| Total                                                                                                  | $ 4,006,753     |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Total                                                                                                  | 1.71%           |   |   |
| U.S. government agencies - Commercial                                                                  |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 0             |   |   |
| Due after 1 year but within 5 years                                                                    | 0               |   |   |
| Due after 5 years but within 10 years                                                                  | 0               |   |   |
| Due After 10 Years/No Maturity                                                                         | 1,002,355       |   |   |
| Total                                                                                                  | $ 1,002,355     |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Total                                                                                                  | 2.24%           |   |   |
| FHLMC and FNMA - Residential debt securities                                                           |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 0             |   |   |
| Due after 1 year but within 5 years                                                                    | 5,916           |   |   |
| Due after 5 years but within 10 years                                                                  | 270,989         |   |   |
| Due After 10 Years/No Maturity                                                                         | 8,217,268       |   |   |
| Total                                                                                                  | $ 8,494,173     |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Total                                                                                                  | 2.01%           |   |   |
| FHLMC and FNMA - Commercial debt securities                                                            |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 0             |   |   |
| Due after 1 year but within 5 years                                                                    | 7,755           |   |   |
| Due after 5 years but within 10 years                                                                  | 25,348          |   |   |
| Due After 10 Years/No Maturity                                                                         | 103,227         |   |   |
| Total                                                                                                  | $ 136,330       |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Total                                                                                                  | 2.90%           |   |   |
| Non-agency securities                                                                                  |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 0             |   |   |
| Due after 1 year but within 5 years                                                                    | 45              |   |   |
| Due after 5 years but within 10 years                                                                  | 0               |   |   |
| Due After 10 Years/No Maturity                                                                         | 0               |   |   |
| Total                                                                                                  | $ 45            |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Total                                                                                                  | 3.35%           |   |   |
| Debt Securities                                                                                        |            |   |   |
| **Fair Value**                                                                                         |            |   |   |
| Due within one year                                                                                    | $ 769,817       |   |   |
| Due after 1 year but within 5 years                                                                    | 5,472,192       |   |   |
| Due after 5 years but within 10 years                                                                  | 527,425         |   |   |
| Due After 10 Years/No Maturity                                                                         | 14,071,574      |   |   |
| Total                                                                                                  | $ 20,841,008    |   |   |
| **Weighted Average Yield**                                                                             |            |   |   |
| Due Within One Year                                                                                    | 1.09%           |   |   |
| Due After 1 Within 5 Years                                                                             | 1.43%           |   |   |
| Due After 5 Within 10 Years                                                                            | 1.94%           |   |   |
| Due After 10 Years/No Maturity                                                                         | 1.99%           |   |   |
| Total                                                                                                  | 1.81%           |   |   |
| **Amortized Cost**                                                                                     |            |   |   |
| Due within one year                                                                                    | $ 773,150       |   |   |
| Due after 1 year but within 5 years                                                                    | 5,466,760       |   |   |
| Due after 5 years but within 10 years                                                                  | 525,590         |   |   |
| Due After 10 Years/No Maturity                                                                         | 14,229,672      |   |   |
| Total                                                                                                  | $ 20,995,172    |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of available-for-sale debt securities at cost, net of adjustments, maturing after the tenth fiscal year following the latest fiscal year or securities with no maturity date. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.
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| - Definition
Amount of available-for-sale debt securities at fair value maturing after the tenth fiscal year following the latest fiscal year or securities with no maturity date.
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No definition available.
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Available-for-sale Securities, Debt Maturities, After Ten Years without Maturity Date, Weighted Average Yield
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| - Definition
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Weighted Average Yield
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Available-for-sale Securities, Debt Maturities, Weighted Average Yield
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Available-for-sale Securities, Debt Maturities, Weighted Average Yield [Abstract]
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| X                                                                                                                                                                                                                                                                                                                                                        |
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| - Definition
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Weighted Average Yield
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Available-for-sale Securities, Debt Maturity, Year Two Through Five, Weighted Average Yield
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| - Definition
This item represents the cost of debt 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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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount after adjustments of available-for-sale debt securities at cost, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of available-for-sale debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount after adjustments of available-for-sale debt securities at cost, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.
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| - Definition
Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.
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| - Definition
Amount after adjustments of available-for-sale debt securities at cost, maturing in the next fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.
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| - Definition
Fair value of available-for-sale debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.
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| - Definition
Amount of debt securities categorized neither as held-to-maturity nor trading.
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| - Definition
Percentage of domestic federal statutory tax rate applicable to pretax income (loss).
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