SECURITIES - Summary of Residential Securities and CMBS (Details) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($)
Debt Securities, Available-For-Sale [Roll Forward]
Beginning balance	$ 114,833,580
Purchases	11,925,383
Sales and transfers	(42,333,457)
Principal paydowns	(4,890,854)
(Amortization) / accretion	(616,847)
Fair value adjustment	439,791
Ending balance	79,357,596
Residential Securities
Debt Securities, Available-For-Sale [Roll Forward]
Beginning balance	114,560,557
Purchases	11,925,383
Sales and transfers	(42,179,748)
Principal paydowns	(4,885,921)
(Amortization) / accretion	(616,974)
Fair value adjustment	462,374
Ending balance	79,265,671
Commercial Securities
Debt Securities, Available-For-Sale [Roll Forward]
Beginning balance	273,023
Purchases	0
Sales and transfers	(153,709)
Principal paydowns	(4,933)
(Amortization) / accretion	127
Fair value adjustment	(22,583)
Ending balance	$ 91,925

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Debt Securities, Available-For-Sale [Roll Forward]

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Proceeds from Sale of Debt Securities, Available-for-sale, Excluding Variable Interest Entity

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

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Amount of cash inflow from sale, maturity, prepayment and call of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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