SECURITIES - Portfolio (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	$ 83,718,342	$ 65,793,672
Remaining Premium	3,330,873	3,771,429
Remaining Discount	(846,235)	(77,850)
Amortized Cost	73,744,471	62,903,483
Unrealized Gains	25,104	1,425,965
Unrealized Losses	(6,930,222)	(673,774)
Estimated Fair Value	66,839,353	63,655,674
Total Residential Securities
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	83,106,761	65,260,601
Remaining Premium	3,330,873	3,771,429
Remaining Discount	(843,030)	(77,723)
Amortized Cost	73,136,095	62,370,539
Unrealized Gains	25,104	1,425,800
Unrealized Losses	(6,910,346)	(671,170)
Estimated Fair Value	66,250,853	63,125,169
Agency
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	75,993,078	62,472,356
Remaining Premium	3,282,681	3,745,824
Remaining Discount	(728,995)	(20,438)
Amortized Cost	69,722,785	59,794,582
Unrealized Gains	11,677	1,386,383
Unrealized Losses	(6,697,221)	(655,360)
Estimated Fair Value	63,037,241	60,525,605
Agency | Fixed-rate pass-through
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	65,429,709	54,432,252
Remaining Premium	2,561,532	3,008,185
Remaining Discount	(727,852)	(18,314)
Amortized Cost	67,263,389	57,422,123
Unrealized Gains	7,680	1,349,125
Unrealized Losses	(6,289,954)	(474,643)
Estimated Fair Value	60,981,115	58,296,605
Agency | Adjustable-rate pass-through
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	243,262	305,211
Remaining Premium	14,340	1,965
Remaining Discount	(98)	(2,124)
Amortized Cost	257,504	305,052
Unrealized Gains	3,738	16,223
Unrealized Losses	(11,738)	(2)
Estimated Fair Value	249,504	321,273
Agency | CMO
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	103,521	114,533
Remaining Premium	1,795	1,888
Remaining Discount	0	0
Amortized Cost	105,316	116,421
Unrealized Gains	0	5,277
Unrealized Losses	(12,996)	0
Estimated Fair Value	92,320	121,698
Agency | Interest-only
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	1,576,498	1,912,415
Remaining Premium	400,101	456,683
Remaining Discount	0	0
Amortized Cost	400,101	456,683
Unrealized Gains	259	428
Unrealized Losses	(227,515)	(163,197)
Estimated Fair Value	172,845	293,914
Agency | Multifamily
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	8,610,998	5,671,138
Remaining Premium	301,545	273,553
Remaining Discount	(1,045)	0
Amortized Cost	1,664,017	1,453,946
Unrealized Gains	0	15,330
Unrealized Losses	(151,917)	(16,563)
Estimated Fair Value	1,512,100	1,452,713
Agency | Reverse mortgages
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	29,090	36,807
Remaining Premium	3,368	3,550
Remaining Discount	0	0
Amortized Cost	32,458	40,357
Unrealized Gains	0	0
Unrealized Losses	(3,101)	(955)
Estimated Fair Value	29,357	39,402
Agency | Multifamily Interest-Only Security
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	7,200,000	4,500,000
Residential credit
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	7,113,683	2,788,245
Remaining Premium	48,192	25,605
Remaining Discount	(114,035)	(57,285)
Amortized Cost	3,413,310	2,575,957
Unrealized Gains	13,427	39,417
Unrealized Losses	(213,125)	(15,810)
Estimated Fair Value	3,213,612	2,599,564
Residential credit | Credit risk transfer
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	1,100,944	924,101
Remaining Premium	7,170	8,754
Remaining Discount	(4,385)	(1,176)
Amortized Cost	1,103,729	927,555
Unrealized Gains	900	9,641
Unrealized Losses	(47,723)	(968)
Estimated Fair Value	1,056,906	936,228
Residential credit | Alt-A
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	145,718	83,213
Remaining Premium	31	31
Remaining Discount	(20,012)	(17,133)
Amortized Cost	125,737	66,111
Unrealized Gains	1,731	3,627
Unrealized Losses	(9,624)	(251)
Estimated Fair Value	117,844	69,487
Residential credit | Prime
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	2,038,622	323,062
Remaining Premium	21,762	9,841
Remaining Discount	(25,159)	(14,757)
Amortized Cost	300,186	268,117
Unrealized Gains	5,440	10,853
Unrealized Losses	(42,791)	(3,529)
Estimated Fair Value	262,835	275,441
Residential credit | Subprime
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	206,413	170,671
Remaining Premium	207	349
Remaining Discount	(19,387)	(16,111)
Amortized Cost	187,233	154,909
Unrealized Gains	3,242	8,285
Unrealized Losses	(12,656)	(118)
Estimated Fair Value	177,819	163,076
Residential credit | NPL/RPL
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	1,456,013	987,415
Remaining Premium	1,695	950
Remaining Discount	(15,580)	(1,698)
Amortized Cost	1,442,128	986,667
Unrealized Gains	0	2,739
Unrealized Losses	(58,640)	(5,968)
Estimated Fair Value	1,383,488	983,438
Residential credit | Prime jumbo (>=2010 vintage)
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	2,165,973	299,783
Remaining Premium	17,327	5,680
Remaining Discount	(29,512)	(6,410)
Amortized Cost	254,297	172,598
Unrealized Gains	2,114	4,272
Unrealized Losses	(41,691)	(4,976)
Estimated Fair Value	214,720	171,894
Residential credit | CRT interest-only security
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	0	4,100
Residential credit | Prime interest-only
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	1,700,000	50,000
Residential credit | Prime Jumbo interest-only
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	1,900,000	126,500
Commercial Securities
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	611,581	533,071
Remaining Premium	0	0
Remaining Discount	(3,205)	(127)
Amortized Cost	608,376	532,944
Unrealized Gains	0	165
Unrealized Losses	(19,876)	(2,604)
Estimated Fair Value	$ 588,500	$ 530,505