SECURITIES - Summary of Residential Securities and CMBS (Details) $ in Thousands	9 Months Ended
Sep. 30, 2019 USD ($)
Debt Securities, Available-For-Sale [Line Items]
Beginning balance	$ 92,623,788
Purchases	51,093,826
Sales	(19,886,088)
Principal paydowns	(11,258,324)
(Amortization) / accretion	(941,881)
Fair value adjustment	4,462,740
Ending balance	116,094,061
Residential Securities
Debt Securities, Available-For-Sale [Line Items]
Beginning balance	92,467,030
Purchases	50,982,244
Sales	(19,793,722)
Principal paydowns	(11,215,154)
(Amortization) / accretion	(942,429)
Fair value adjustment	4,455,241
Ending balance	115,953,210
Commercial Securities
Debt Securities, Available-For-Sale [Line Items]
Beginning balance	156,758
Purchases	111,582
Sales	(92,366)
Principal paydowns	(43,170)
(Amortization) / accretion	548
Fair value adjustment	7,499
Ending balance	$ 140,851

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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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