Securities - Schedule of Debt Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
AFS debt securities:
Amortized Cost	$ 12,962,469	$ 11,505,775
Gross Unrealized Gains	27,372	15,273
Gross Unrealized Losses	(604,929)	(674,237)
Fair Value	12,384,912	10,846,811
HTM debt securities:
Amortized Cost	2,905,341	2,917,413
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(470,049)	(529,659)
Fair Value	2,435,292	2,387,754
Total debt securities
Amortized Cost	15,867,810	14,423,188
Gross Unrealized Gains	27,372	15,273
Gross Unrealized Losses	(1,074,978)	(1,203,896)
Fair Value	14,820,204	13,234,565
AFS and HTM, accrued interest	44,000	45,000
Government National Mortgage Association (GNMA)
AFS debt securities:
Amortized Cost	8,600,000	7,300,000
Fair Value	8,500,000	7,200,000
HTM debt securities:
Amortized Cost	84,000	86,000
Fair Value	68,000	68,000
U.S. Treasury securities
AFS debt securities:
Amortized Cost	961,291	676,300
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(30,310)	(38,035)
Fair Value	930,981	638,265
HTM debt securities:
Amortized Cost	536,459	535,080
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(27,846)	(35,222)
Fair Value	508,613	499,858
U.S. government agency and U.S. government-sponsored enterprise debt securities
AFS debt securities:
Amortized Cost	306,428	308,220
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(38,022)	(45,633)
Fair Value	268,406	262,587
HTM debt securities:
Amortized Cost	1,005,347	1,004,479
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(173,991)	(200,259)
Fair Value	831,356	804,220
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	455,534	472,535
Gross Unrealized Gains	2,616	886
Gross Unrealized Losses	(39,600)	(47,207)
Fair Value	418,550	426,214
HTM debt securities:
Amortized Cost	481,507	486,388
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(78,425)	(91,461)
Fair Value	403,082	394,927
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
AFS debt securities:
Amortized Cost	9,204,823	7,974,768
Gross Unrealized Gains	23,770	12,278
Gross Unrealized Losses	(223,031)	(248,786)
Fair Value	9,005,562	7,738,260
HTM debt securities:
Amortized Cost	694,808	703,833
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(141,240)	(155,626)
Fair Value	553,568	548,207
Municipal securities
AFS debt securities:
Amortized Cost	286,374	287,301
Gross Unrealized Gains	0	38
Gross Unrealized Losses	(40,520)	(37,186)
Fair Value	245,854	250,153
HTM debt securities:
Amortized Cost	187,220	187,633
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(48,547)	(47,091)
Fair Value	138,673	140,542
Non-agency commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	268,913	294,235
Gross Unrealized Gains	1	2
Gross Unrealized Losses	(32,314)	(35,767)
Fair Value	236,600	258,470
Non-agency residential mortgage-backed securities
AFS debt securities:
Amortized Cost	502,410	514,527
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(72,342)	(80,919)
Fair Value	430,068	433,608
Corporate debt securities
AFS debt securities:
Amortized Cost	653,500	653,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(116,958)	(127,334)
Fair Value	536,542	526,166
Foreign government bonds
AFS debt securities:
Amortized Cost	244,459	244,803
Gross Unrealized Gains	985	2,069
Gross Unrealized Losses	(11,253)	(12,992)
Fair Value	234,191	233,880
Asset-backed securities
AFS debt securities:
Amortized Cost	34,237	35,086
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(502)	(371)
Fair Value	33,735	34,715
Collateralized loan obligations (“CLOs”)
AFS debt securities:
Amortized Cost	44,500	44,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(77)	(7)
Fair Value	$ 44,423	$ 44,493