SECURITIES - Summary of Residential Securities and CMBS (Details) $ in Thousands	6 Months Ended
Jun. 30, 2019 USD ($)
Debt Securities, Available-For-Sale [Line Items]
Beginning balance	$ 92,623,788
Purchases	50,123,242
Sales	(19,641,265)
Principal paydowns	(6,105,818)
(Amortization) / accretion	(565,722)
Fair value adjustment	3,492,644
Ending balance	119,926,869
Residential Securities
Debt Securities, Available-For-Sale [Line Items]
Beginning balance	92,467,030
Purchases	50,015,524
Sales	(19,548,899)
Principal paydowns	(6,062,713)
(Amortization) / accretion	(566,071)
Fair value adjustment	3,486,890
Ending balance	119,791,761
Commercial Securities
Debt Securities, Available-For-Sale [Line Items]
Beginning balance	156,758
Purchases	107,718
Sales	(92,366)
Principal paydowns	(43,105)
(Amortization) / accretion	349
Fair value adjustment	5,754
Ending balance	$ 135,108

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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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