SECURITIES - Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	$ 90,400,391	$ 86,183,782
Remaining Premium	2,937,481	2,943,297
Remaining Discount	(1,243,353)	(1,110,917)
Amortized Cost	72,473,602	70,669,855
Unrealized Gains	227,203	83,143
Unrealized Losses	(3,462,620)	(4,963,091)
Estimated Fair Value	69,238,185	65,789,907
Total residential securities
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	89,881,827	85,637,283
Remaining Premium	2,937,481	2,943,297
Remaining Discount	(1,241,523)	(1,108,512)
Amortized Cost	71,956,868	70,125,761
Unrealized Gains	227,203	83,143
Unrealized Losses	(3,446,497)	(4,945,306)
Estimated Fair Value	68,737,574	65,263,598
Agency
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	78,131,936	75,220,242
Remaining Premium	2,856,175	2,878,118
Remaining Discount	(1,117,615)	(1,004,331)
Amortized Cost	68,674,734	66,908,288
Unrealized Gains	206,341	71,939
Unrealized Losses	(3,257,541)	(4,705,332)
Estimated Fair Value	65,623,534	62,274,895
Agency | Fixed-rate pass-through
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	64,851,694	63,232,479
Remaining Premium	2,009,496	2,105,813
Remaining Discount	(1,116,103)	(1,003,225)
Amortized Cost	65,745,087	64,335,067
Unrealized Gains	185,694	62,060
Unrealized Losses	(2,978,073)	(4,367,369)
Estimated Fair Value	62,952,708	60,029,758
Agency | Adjustable-rate pass-through
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	221,651	232,028
Remaining Premium	16,768	17,065
Remaining Discount	(78)	(85)
Amortized Cost	238,341	249,008
Unrealized Gains	2,226	2,138
Unrealized Losses	(15,695)	(16,759)
Estimated Fair Value	224,872	234,387
Agency | CMO
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	99,729	101,543
Remaining Premium	1,752	1,781
Remaining Discount	0	0
Amortized Cost	101,481	103,324
Unrealized Gains	0	0
Unrealized Losses	(11,793)	(13,714)
Estimated Fair Value	89,688	89,610
Agency | Interest-only
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	2,347,144	1,824,339
Remaining Premium	507,374	438,295
Remaining Discount	0	0
Amortized Cost	507,374	438,295
Unrealized Gains	3,675	153
Unrealized Losses	(196,486)	(220,371)
Estimated Fair Value	314,563	218,077
Agency | Multifamily
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	10,584,134	9,801,375
Remaining Premium	317,435	311,785
Remaining Discount	(1,434)	(1,021)
Amortized Cost	2,051,517	1,750,737
Unrealized Gains	14,746	7,588
Unrealized Losses	(52,824)	(84,160)
Estimated Fair Value	2,013,439	1,674,165
Agency | Reverse mortgages
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	27,584	28,478
Remaining Premium	3,350	3,379
Remaining Discount	0	0
Amortized Cost	30,934	31,857
Unrealized Gains	0	0
Unrealized Losses	(2,670)	(2,959)
Estimated Fair Value	28,264	28,898
Agency | Multifamily Interest-Only Security
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	8,800,000	8,400,000
Residential credit
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	11,749,891	10,417,041
Remaining Premium	81,306	65,179
Remaining Discount	(123,908)	(104,181)
Amortized Cost	3,282,134	3,217,473
Unrealized Gains	20,862	11,204
Unrealized Losses	(188,956)	(239,974)
Estimated Fair Value	3,114,040	2,988,703
Residential credit | Credit risk transfer
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	1,087,475	1,013,368
Remaining Premium	6,626	6,790
Remaining Discount	(5,184)	(4,828)
Amortized Cost	1,088,917	1,015,330
Unrealized Gains	10,154	6,629
Unrealized Losses	(13,687)	(24,402)
Estimated Fair Value	1,085,384	997,557
Residential credit | Alt-A
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	118,110	111,009
Remaining Premium	9	9
Remaining Discount	(5,027)	(5,048)
Amortized Cost	113,092	105,970
Unrealized Gains	0	0
Unrealized Losses	(11,523)	(14,754)
Estimated Fair Value	101,569	91,216
Residential credit | Prime
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	863,323	1,946,186
Remaining Premium	9,725	19,496
Remaining Discount	(24,769)	(17,375)
Amortized Cost	248,242	240,694
Unrealized Gains	2,157	1,528
Unrealized Losses	(38,528)	(44,352)
Estimated Fair Value	211,871	197,870
Residential credit | Subprime
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	206,842	202,304
Remaining Premium	0	0
Remaining Discount	(32,450)	(32,188)
Amortized Cost	174,392	170,116
Unrealized Gains	3,711	1,275
Unrealized Losses	(15,949)	(15,078)
Estimated Fair Value	162,154	156,313
Residential credit | NPL/RPL
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	1,328,628	1,426,616
Remaining Premium	2,796	1,624
Remaining Discount	(15,948)	(15,500)
Amortized Cost	1,315,476	1,412,740
Unrealized Gains	1,109	87
Unrealized Losses	(67,660)	(95,673)
Estimated Fair Value	1,248,925	1,317,154
Residential credit | Prime jumbo (>=2010 vintage)
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	8,145,513	5,717,558
Remaining Premium	62,150	37,260
Remaining Discount	(40,530)	(29,242)
Amortized Cost	342,015	272,623
Unrealized Gains	3,731	1,685
Unrealized Losses	(41,609)	(45,715)
Estimated Fair Value	304,137	228,593
Residential credit | Prime interest-only
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	600,000	1,700,000
Residential credit | Prime Jumbo interest-only
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	7,800,000	5,500,000
Commercial Securities
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	518,564	546,499
Remaining Premium	0	0
Remaining Discount	(1,830)	(2,405)
Amortized Cost	516,734	544,094
Unrealized Gains	0	0
Unrealized Losses	(16,123)	(17,785)
Estimated Fair Value	$ 500,611	$ 526,309