Securities - Schedule of Debt Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
AFS debt securities:
Amortized Cost	$ 6,891,522	$ 10,087,179
Gross Unrealized Gains	1,340	51,025
Gross Unrealized Losses	(637,358)	(172,851)
Fair Value	6,255,504	9,965,353
HTM debt securities:
Amortized Cost	3,028,302	0
Gross Unrealized Gains	0
Gross Unrealized Losses	(371,753)
Fair Value	2,656,549
Total debt securities
Amortized Cost	9,919,824
Gross Unrealized Gains	1,340
Gross Unrealized Losses	(1,009,111)
Fair Value	8,912,053
U.S. Treasury securities
AFS debt securities:
Amortized Cost	676,320	1,049,238
Gross Unrealized Gains	0	130
Gross Unrealized Losses	(51,634)	(16,687)
Fair Value	624,686	1,032,681
HTM debt securities:
Amortized Cost	521,352
Gross Unrealized Gains	0
Gross Unrealized Losses	(34,831)
Fair Value	486,521
U.S. government agency and U.S. government-sponsored enterprise debt securities
AFS debt securities:
Amortized Cost	324,463	1,333,984
Gross Unrealized Gains	0	2,697
Gross Unrealized Losses	(39,218)	(34,710)
Fair Value	285,245	1,301,971
HTM debt securities:
Amortized Cost	997,369
Gross Unrealized Gains	0
Gross Unrealized Losses	(144,291)
Fair Value	853,078
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	614,135	1,242,043
Gross Unrealized Gains	125	15,791
Gross Unrealized Losses	(50,428)	(28,854)
Fair Value	563,832	1,228,980
HTM debt securities:
Amortized Cost	512,391
Gross Unrealized Gains	0
Gross Unrealized Losses	(62,563)
Fair Value	449,828
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
AFS debt securities:
Amortized Cost	2,097,339	2,968,789
Gross Unrealized Gains	193	8,629
Gross Unrealized Losses	(187,292)	(49,135)
Fair Value	1,910,240	2,928,283
HTM debt securities:
Amortized Cost	807,111
Gross Unrealized Gains	0
Gross Unrealized Losses	(96,637)
Fair Value	710,474
Municipal securities
AFS debt securities:
Amortized Cost	306,419	519,381
Gross Unrealized Gains	22	10,065
Gross Unrealized Losses	(39,708)	(6,288)
Fair Value	266,733	523,158
HTM debt securities:
Amortized Cost	190,079
Gross Unrealized Gains	0
Gross Unrealized Losses	(33,431)
Fair Value	156,648
Non-agency commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	451,200	498,920
Gross Unrealized Gains	247	3,000
Gross Unrealized Losses	(39,679)	(5,477)
Fair Value	411,768	496,443
Non-agency residential mortgage-backed securities
AFS debt securities:
Amortized Cost	808,012	889,937
Gross Unrealized Gains	0	971
Gross Unrealized Losses	(81,023)	(8,977)
Fair Value	726,989	881,931
Corporate debt securities
AFS debt securities:
Amortized Cost	673,502	657,516
Gross Unrealized Gains	105	8,738
Gross Unrealized Losses	(114,314)	(16,589)
Fair Value	559,293	649,665
Foreign government bonds
AFS debt securities:
Amortized Cost	253,118	260,447
Gross Unrealized Gains	648	767
Gross Unrealized Losses	(10,769)	(3,481)
Fair Value	242,997	257,733
Asset-backed securities
AFS debt securities:
Amortized Cost	69,764	74,674
Gross Unrealized Gains	0	185
Gross Unrealized Losses	(2,414)	(301)
Fair Value	67,350	74,558
Collateralized loan obligations (“CLOs”)
AFS debt securities:
Amortized Cost	617,250	592,250
Gross Unrealized Gains	0	52
Gross Unrealized Losses	(20,879)	(2,352)
Fair Value	$ 596,371	$ 589,950