Securities - Schedule of Available-for-sale and Held-to-maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
AFS debt securities:
Amortized Cost	$ 6,916,491	$ 6,879,225
Gross Unrealized Gains	783	498
Gross Unrealized Losses	(728,937)	(844,730)
Fair Value	6,188,337	6,034,993
HTM debt securities
Amortized Cost	2,956,040	3,001,868
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(502,069)	(546,697)
Fair Value	2,453,971	2,455,171
Total debt securities
Amortized Cost	9,872,531	9,881,093
Gross Unrealized Gains	783	498
Gross Unrealized Losses	(1,231,006)	(1,391,427)
Fair Value	8,642,308	8,490,164
U.S. Treasury securities
AFS debt securities:
Amortized Cost	1,112,587	676,306
Gross Unrealized Gains	101	0
Gross Unrealized Losses	(52,313)	(70,103)
Fair Value	1,060,375	606,203
HTM debt securities
Amortized Cost	529,548	524,081
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(40,997)	(52,612)
Fair Value	488,551	471,469
U.S. government agency and U.S. government-sponsored enterprise debt securities
AFS debt securities:
Amortized Cost	412,086	517,806
Gross Unrealized Gains	0	67
Gross Unrealized Losses	(47,640)	(56,266)
Fair Value	364,446	461,607
HTM debt securities
Amortized Cost	1,001,836	998,972
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(186,904)	(209,560)
Fair Value	814,932	789,412
US government agencies And U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	531,377	577,392
Gross Unrealized Gains	158	0
Gross Unrealized Losses	(63,276)	(77,123)
Fair Value	468,259	500,269
HTM debt securities
Amortized Cost	493,348	506,965
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(88,968)	(98,566)
Fair Value	404,380	408,399
US government agencies And U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
AFS debt securities:
Amortized Cost	1,956,927	2,011,054
Gross Unrealized Gains	380	41
Gross Unrealized Losses	(229,713)	(248,900)
Fair Value	1,727,594	1,762,195
HTM debt securities
Amortized Cost	742,436	782,141
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(142,119)	(148,230)
Fair Value	600,317	633,911
Municipal securities:
AFS debt securities:
Amortized Cost	297,283	303,884
Gross Unrealized Gains	75	3
Gross Unrealized Losses	(36,342)	(46,788)
Fair Value	261,016	257,099
HTM debt securities
Amortized Cost	188,872	189,709
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(43,081)	(37,729)
Fair Value	145,791	151,980
Non-agency commercial mortgage-backed Securities
AFS debt securities:
Amortized Cost	409,578	447,512
Gross Unrealized Gains	0	213
Gross Unrealized Losses	(42,062)	(49,396)
Fair Value	367,516	398,329
Non-agency residential mortgage-backed Securities
AFS debt securities:
Amortized Cost	643,335	762,202
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(89,664)	(112,978)
Fair Value	553,671	649,224
Corporate debt securities
AFS debt securities:
Amortized Cost	653,501	673,502
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(151,076)	(147,228)
Fair Value	502,425	526,274
Foreign government bonds
AFS debt securities:
Amortized Cost	239,333	241,165
Gross Unrealized Gains	69	174
Gross Unrealized Losses	(11,528)	(14,286)
Fair Value	227,874	227,053
Asset-backed securities
AFS debt securities:
Amortized Cost	43,234	51,152
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(934)	(2,076)
Fair Value	42,300	49,076
CLOs
AFS debt securities:
Amortized Cost	617,250	617,250
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4,389)	(19,586)
Fair Value	$ 612,861	$ 597,664