Securities - Schedule of Debt Securities (Details) - USD ($)	Sep. 30, 2025	Dec. 31, 2024
AFS debt securities:
Amortized Cost	$ 13,189,313,000	$ 11,505,775,000
Gross Unrealized Gains	58,082,000	15,273,000
Gross Unrealized Losses	(503,243,000)	(674,237,000)
Allowance for Credit Losses	(3,000,000)	0
Fair Value	12,741,152,000	10,846,811,000
HTM debt securities:
Amortized Cost	2,880,682,000	2,917,413,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(413,320,000)	(529,659,000)
Allowance for Credit Losses	0	0
Fair Value	2,467,362,000	2,387,754,000
Total debt securities
Amortized Cost	16,069,995,000	14,423,188,000
Gross Unrealized Gains	58,082,000	15,273,000
Gross Unrealized Losses	(916,563,000)	(1,203,896,000)
Allowance for Credit Losses	(3,000,000)
Fair Value	15,208,514,000	13,234,565,000
AFS and HTM, accrued interest	47,000,000	45,000,000
Government National Mortgage Association (GNMA)
AFS debt securities:
Amortized Cost	9,100,000,000	7,300,000,000
Fair Value	9,100,000,000	7,200,000,000
HTM debt securities:
Amortized Cost	81,000,000	86,000,000
Fair Value	66,000,000	68,000,000
U.S. Treasury securities
AFS debt securities:
Amortized Cost	875,577,000	676,300,000
Gross Unrealized Gains	640,000	0
Gross Unrealized Losses	(20,002,000)	(38,035,000)
Allowance for Credit Losses	0
Fair Value	856,215,000	638,265,000
HTM debt securities:
Amortized Cost	539,255,000	535,080,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(19,455,000)	(35,222,000)
Allowance for Credit Losses	0
Fair Value	519,800,000	499,858,000
U.S. government agency and U.S. government-sponsored enterprise debt securities
AFS debt securities:
Amortized Cost	288,368,000	308,220,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(31,982,000)	(45,633,000)
Allowance for Credit Losses	0
Fair Value	256,386,000	262,587,000
HTM debt securities:
Amortized Cost	1,006,602,000	1,004,479,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(152,505,000)	(200,259,000)
Allowance for Credit Losses	0
Fair Value	854,097,000	804,220,000
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	359,373,000	472,535,000
Gross Unrealized Gains	97,000	886,000
Gross Unrealized Losses	(31,039,000)	(47,207,000)
Allowance for Credit Losses	0
Fair Value	328,431,000	426,214,000
HTM debt securities:
Amortized Cost	476,530,000	486,388,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(71,706,000)	(91,461,000)
Allowance for Credit Losses	0
Fair Value	404,824,000	394,927,000
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
AFS debt securities:
Amortized Cost	9,816,928,000	7,974,768,000
Gross Unrealized Gains	56,707,000	12,278,000
Gross Unrealized Losses	(190,200,000)	(248,786,000)
Allowance for Credit Losses	0
Fair Value	9,683,435,000	7,738,260,000
HTM debt securities:
Amortized Cost	672,283,000	703,833,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(129,010,000)	(155,626,000)
Allowance for Credit Losses	0
Fair Value	543,273,000	548,207,000
Municipal securities
AFS debt securities:
Amortized Cost	282,015,000	287,301,000
Gross Unrealized Gains	21,000	38,000
Gross Unrealized Losses	(36,854,000)	(37,186,000)
Allowance for Credit Losses	0
Fair Value	245,182,000	250,153,000
HTM debt securities:
Amortized Cost	186,012,000	187,633,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(40,644,000)	(47,091,000)
Allowance for Credit Losses	0
Fair Value	145,368,000	140,542,000
Non-agency commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	224,699,000	294,235,000
Gross Unrealized Gains	0	2,000
Gross Unrealized Losses	(23,706,000)	(35,767,000)
Allowance for Credit Losses	(3,000,000)
Fair Value	197,993,000	258,470,000
Non-agency residential mortgage-backed securities
AFS debt securities:
Amortized Cost	466,826,000	514,527,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(63,148,000)	(80,919,000)
Allowance for Credit Losses	0
Fair Value	403,678,000	433,608,000
Corporate debt securities
AFS debt securities:
Amortized Cost	596,900,000	653,500,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(96,030,000)	(127,334,000)
Allowance for Credit Losses	0
Fair Value	500,870,000	526,166,000
Foreign government bonds
AFS debt securities:
Amortized Cost	245,978,000	244,803,000
Gross Unrealized Gains	617,000	2,069,000
Gross Unrealized Losses	(9,576,000)	(12,992,000)
Allowance for Credit Losses	0
Fair Value	237,019,000	233,880,000
Asset-backed securities
AFS debt securities:
Amortized Cost	32,649,000	35,086,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(706,000)	(371,000)
Allowance for Credit Losses	0
Fair Value	$ 31,943,000	34,715,000
Collateralized loan obligations (“CLOs”)
AFS debt securities:
Amortized Cost		44,500,000
Gross Unrealized Gains		0
Gross Unrealized Losses		(7,000)
Fair Value		$ 44,493,000