Securities - Schedule of Debt Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
AFS debt securities:
Amortized Cost	$ 6,820,569	$ 6,879,225
Gross Unrealized Gains	212	498
Gross Unrealized Losses	(833,523)	(844,730)
Fair Value	5,987,258	6,034,993
HTM debt securities:
Amortized Cost	2,975,933	3,001,868
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(535,449)	(546,697)
Fair Value	2,440,484	2,455,171
Total debt securities
Amortized Cost	9,796,502	9,881,093
Gross Unrealized Gains	212	498
Gross Unrealized Losses	(1,368,972)	(1,391,427)
Fair Value	8,427,742	8,490,164
U.S. Treasury securities
AFS debt securities:
Amortized Cost	779,973	676,306
Gross Unrealized Gains	15	0
Gross Unrealized Losses	(68,282)	(70,103)
Fair Value	711,706	606,203
HTM debt securities:
Amortized Cost	526,794	524,081
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(52,657)	(52,612)
Fair Value	474,137	471,469
U.S. government agency and U.S. government-sponsored enterprise debt securities
AFS debt securities:
Amortized Cost	514,594	517,806
Gross Unrealized Gains	0	67
Gross Unrealized Losses	(54,510)	(56,266)
Fair Value	460,084	461,607
HTM debt securities:
Amortized Cost	1,000,415	998,972
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(202,544)	(209,560)
Fair Value	797,871	789,412
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	552,859	577,392
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(74,082)	(77,123)
Fair Value	478,777	500,269
HTM debt securities:
Amortized Cost	496,852	506,965
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(93,114)	(98,566)
Fair Value	403,738	408,399
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
AFS debt securities:
Amortized Cost	1,966,906	2,011,054
Gross Unrealized Gains	15	41
Gross Unrealized Losses	(245,684)	(248,900)
Fair Value	1,721,237	1,762,195
HTM debt securities:
Amortized Cost	762,573	782,141
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(147,285)	(148,230)
Fair Value	615,288	633,911
Municipal securities
AFS debt securities:
Amortized Cost	304,204	303,884
Gross Unrealized Gains	28	3
Gross Unrealized Losses	(40,359)	(46,788)
Fair Value	263,873	257,099
HTM debt securities:
Amortized Cost	189,299	189,709
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(39,849)	(37,729)
Fair Value	149,450	151,980
Non-agency commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	432,782	447,512
Gross Unrealized Gains	2	213
Gross Unrealized Losses	(48,733)	(49,396)
Fair Value	384,051	398,329
Non-agency residential mortgage-backed securities
AFS debt securities:
Amortized Cost	715,775	762,202
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(107,201)	(112,978)
Fair Value	608,574	649,224
Corporate debt securities
AFS debt securities:
Amortized Cost	653,502	673,502
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(167,752)	(147,228)
Fair Value	485,750	526,274
Foreign government bonds
AFS debt securities:
Amortized Cost	236,392	241,165
Gross Unrealized Gains	152	174
Gross Unrealized Losses	(11,778)	(14,286)
Fair Value	224,766	227,053
Asset-backed securities
AFS debt securities:
Amortized Cost	46,332	51,152
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,457)	(2,076)
Fair Value	44,875	49,076
Collateralized loan obligations (“CLOs”)
AFS debt securities:
Amortized Cost	617,250	617,250
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(13,685)	(19,586)
Fair Value	$ 603,565	$ 597,664