SECURITIES - Portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	$ 94,451,712	$ 86,183,782
Remaining Premium	2,796,454	2,943,297
Remaining Discount	(1,331,965)	(1,110,917)
Amortized Cost	74,986,296	70,669,855
Unrealized Gains	96,042	83,143
Unrealized Losses	(3,879,877)	(4,963,091)
Estimated Fair Value	71,202,461	65,789,907
Total residential securities
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	94,076,348	85,637,283
Remaining Premium	2,796,454	2,943,297
Remaining Discount	(1,330,618)	(1,108,512)
Amortized Cost	74,612,279	70,125,761
Unrealized Gains	95,949	83,143
Unrealized Losses	(3,871,457)	(4,945,306)
Estimated Fair Value	70,836,771	65,263,598
Agency
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	82,177,638	75,220,242
Remaining Premium	2,715,390	2,878,118
Remaining Discount	(1,205,423)	(1,004,331)
Amortized Cost	71,398,163	66,908,288
Unrealized Gains	52,262	71,939
Unrealized Losses	(3,686,161)	(4,705,332)
Estimated Fair Value	67,764,264	62,274,895
Agency | Fixed-rate pass-through
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	68,032,859	63,232,479
Remaining Premium	1,851,124	2,105,813
Remaining Discount	(1,203,805)	(1,003,225)
Amortized Cost	68,680,178	64,335,067
Unrealized Gains	43,777	62,060
Unrealized Losses	(3,375,157)	(4,367,369)
Estimated Fair Value	65,348,798	60,029,758
Agency | Adjustable-rate pass-through
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	209,207	232,028
Remaining Premium	18,434	17,065
Remaining Discount	(69)	(85)
Amortized Cost	227,572	249,008
Unrealized Gains	1,963	2,138
Unrealized Losses	(17,985)	(16,759)
Estimated Fair Value	211,550	234,387
Agency | CMO
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	97,934	101,543
Remaining Premium	1,715	1,781
Remaining Discount	0	0
Amortized Cost	99,649	103,324
Unrealized Gains	0	0
Unrealized Losses	(14,147)	(13,714)
Estimated Fair Value	85,502	89,610
Agency | Interest-only
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	2,308,196	1,824,339
Remaining Premium	492,333	438,295
Remaining Discount	0	0
Amortized Cost	492,333	438,295
Unrealized Gains	1,913	153
Unrealized Losses	(200,727)	(220,371)
Estimated Fair Value	293,519	218,077
Agency | Multifamily
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	11,502,217	9,801,375
Remaining Premium	348,474	311,785
Remaining Discount	(1,549)	(1,021)
Amortized Cost	1,867,896	1,750,737
Unrealized Gains	4,609	7,588
Unrealized Losses	(75,382)	(84,160)
Estimated Fair Value	1,797,123	1,674,165
Agency | Reverse mortgages
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	27,225	28,478
Remaining Premium	3,310	3,379
Remaining Discount	0	0
Amortized Cost	30,535	31,857
Unrealized Gains	0	0
Unrealized Losses	(2,763)	(2,959)
Estimated Fair Value	27,772	28,898
Agency | Multifamily Interest-Only Security
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	10,000,000	8,400,000
Residential credit
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	11,898,710	10,417,041
Remaining Premium	81,064	65,179
Remaining Discount	(125,195)	(104,181)
Amortized Cost	3,214,116	3,217,473
Unrealized Gains	43,687	11,204
Unrealized Losses	(185,296)	(239,974)
Estimated Fair Value	3,072,507	2,988,703
Residential credit | Credit risk transfer
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	1,037,685	1,013,368
Remaining Premium	3,987	6,790
Remaining Discount	(4,686)	(4,828)
Amortized Cost	1,036,986	1,015,330
Unrealized Gains	32,292	6,629
Unrealized Losses	(4,877)	(24,402)
Estimated Fair Value	1,064,401	997,557
Residential credit | Alt-A
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	137,130	111,009
Remaining Premium	9	9
Remaining Discount	(5,054)	(5,048)
Amortized Cost	132,085	105,970
Unrealized Gains	450	0
Unrealized Losses	(13,320)	(14,754)
Estimated Fair Value	119,215	91,216
Residential credit | Prime
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	837,579	1,946,186
Remaining Premium	9,454	19,496
Remaining Discount	(21,866)	(17,375)
Amortized Cost	234,903	240,694
Unrealized Gains	1,488	1,528
Unrealized Losses	(39,778)	(44,352)
Estimated Fair Value	196,613	197,870
Residential credit | Subprime
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	226,613	202,304
Remaining Premium	0	0
Remaining Discount	(30,469)	(32,188)
Amortized Cost	196,144	170,116
Unrealized Gains	2,187	1,275
Unrealized Losses	(17,445)	(15,078)
Estimated Fair Value	180,886	156,313
Residential credit | NPL/RPL
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	1,271,228	1,426,616
Remaining Premium	4,490	1,624
Remaining Discount	(13,052)	(15,500)
Amortized Cost	1,262,666	1,412,740
Unrealized Gains	473	87
Unrealized Losses	(69,789)	(95,673)
Estimated Fair Value	1,193,350	1,317,154
Residential credit | Prime jumbo (>=2010 vintage)
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	8,388,475	5,717,558
Remaining Premium	63,124	37,260
Remaining Discount	(50,068)	(29,242)
Amortized Cost	351,332	272,623
Unrealized Gains	6,797	1,685
Unrealized Losses	(40,087)	(45,715)
Estimated Fair Value	318,042	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	8,100,000	5,500,000
Commercial Securities
Mortgage-Backed Securities Portfolio [Line Items]
Principal / Notional	375,364	546,499
Remaining Premium	0	0
Remaining Discount	(1,347)	(2,405)
Amortized Cost	374,017	544,094
Unrealized Gains	93	0
Unrealized Losses	(8,420)	(17,785)
Estimated Fair Value	$ 365,690	$ 526,309