Securities - Schedule of Debt Securities (Details) - USD ($)	Mar. 31, 2026	Dec. 31, 2025
AFS debt securities:
Amortized Cost	$ 14,546,038,000	$ 13,619,781,000
Gross Unrealized Gains	54,606,000	69,974,000
Gross Unrealized Losses	(507,161,000)	(475,635,000)
Allowance for Credit Losses	0	(1,900,000)
Fair Value	14,093,483,000	13,212,220,000
HTM debt securities:
Amortized Cost	2,858,978,000	2,870,058,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(405,975,000)	(390,312,000)
Allowance for Credit Losses	0	0
Fair Value	2,453,003,000	2,479,746,000
Total debt securities
Amortized Cost	17,405,016,000	16,489,839,000
Gross Unrealized Gains	54,606,000	69,974,000
Gross Unrealized Losses	(913,136,000)	(865,947,000)
Allowance for Credit Losses		(1,900,000)
Fair Value	16,546,486,000	15,691,966,000
AFS and HTM, accrued interest	54,000,000	54,000,000
Government National Mortgage Association (GNMA)
AFS debt securities:
Amortized Cost	10,300,000,000	9,600,000,000
Fair Value	10,300,000,000	9,600,000,000
HTM debt securities:
Amortized Cost	77,000,000	79,000,000
Fair Value	63,000,000	65,000,000
U.S. Treasury securities
AFS debt securities:
Amortized Cost	1,256,350,000	1,010,053,000
Gross Unrealized Gains	495,000	837,000
Gross Unrealized Losses	(19,058,000)	(16,977,000)
Allowance for Credit Losses		0
Fair Value	1,237,787,000	993,913,000
HTM debt securities:
Amortized Cost	542,059,000	540,666,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(16,011,000)	(15,779,000)
Allowance for Credit Losses		0
Fair Value	526,048,000	524,887,000
U.S. government agency and U.S. government-sponsored enterprise debt securities
AFS debt securities:
Amortized Cost	287,503,000	287,687,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(31,640,000)	(30,033,000)
Allowance for Credit Losses		0
Fair Value	255,863,000	257,654,000
HTM debt securities:
Amortized Cost	1,007,937,000	1,007,055,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(152,476,000)	(146,921,000)
Allowance for Credit Losses		0
Fair Value	855,461,000	860,134,000
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	277,947,000	292,564,000
Gross Unrealized Gains	74,000	86,000
Gross Unrealized Losses	(27,359,000)	(27,312,000)
Allowance for Credit Losses		0
Fair Value	250,662,000	265,338,000
HTM debt securities:
Amortized Cost	470,484,000	474,747,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(70,288,000)	(69,471,000)
Allowance for Credit Losses		0
Fair Value	400,196,000	405,276,000
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
AFS debt securities:
Amortized Cost	11,004,372,000	10,251,714,000
Gross Unrealized Gains	53,571,000	68,588,000
Gross Unrealized Losses	(213,506,000)	(187,649,000)
Allowance for Credit Losses		0
Fair Value	10,844,437,000	10,132,653,000
HTM debt securities:
Amortized Cost	653,648,000	662,127,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(125,740,000)	(124,176,000)
Allowance for Credit Losses		0
Fair Value	527,908,000	537,951,000
Municipal securities
AFS debt securities:
Amortized Cost	275,348,000	277,275,000
Gross Unrealized Gains	5,000	20,000
Gross Unrealized Losses	(37,394,000)	(34,193,000)
Allowance for Credit Losses		0
Fair Value	237,959,000	243,102,000
HTM debt securities:
Amortized Cost	184,850,000	185,463,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(41,460,000)	(33,965,000)
Allowance for Credit Losses		0
Fair Value	143,390,000	151,498,000
Non-agency commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	197,286,000	214,987,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(22,416,000)	(22,139,000)
Allowance for Credit Losses		(1,900,000)
Fair Value	174,870,000	190,948,000
Non-agency residential mortgage-backed securities
AFS debt securities:
Amortized Cost	431,846,000	452,208,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(58,349,000)	(58,421,000)
Allowance for Credit Losses		0
Fair Value	373,497,000	393,787,000
Corporate debt securities
AFS debt securities:
Amortized Cost	535,158,000	554,158,000
Gross Unrealized Gains	0	6,000
Gross Unrealized Losses	(87,575,000)	(89,183,000)
Allowance for Credit Losses		0
Fair Value	447,583,000	464,981,000
Foreign government bonds
AFS debt securities:
Amortized Cost	249,263,000	247,249,000
Gross Unrealized Gains	461,000	437,000
Gross Unrealized Losses	(9,329,000)	(9,231,000)
Allowance for Credit Losses		0
Fair Value	240,395,000	238,455,000
Asset-backed securities
AFS debt securities:
Amortized Cost	30,965,000	31,886,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(535,000)	(497,000)
Allowance for Credit Losses		0
Fair Value	$ 30,430,000	$ 31,389,000