Securities - Schedule of Debt Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
AFS debt securities:
Amortized Cost	$ 9,644,377	$ 6,916,491
Gross Unrealized Gains	4,357	783
Gross Unrealized Losses	(725,206)	(728,937)
Fair Value	8,923,528	6,188,337
HTM debt securities:
Amortized Cost	2,938,250	2,956,040
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(533,023)	(502,069)
Fair Value	2,405,227	2,453,971
Total debt securities
Amortized Cost	12,582,627	9,872,531
Gross Unrealized Gains	4,357	783
Gross Unrealized Losses	(1,258,229)	(1,231,006)
Fair Value	11,328,755	8,642,308
AFS and HTM, accrued interest	44,000	44,000
Government National Mortgage Association (GNMA)
AFS debt securities:
Amortized Cost	5,200,000	1,300,000
Fair Value	5,200,000	1,200,000
HTM debt securities:
Amortized Cost	89,000	92,000
Fair Value	71,000	75,000
U.S. Treasury securities
AFS debt securities:
Amortized Cost	676,291	1,112,587
Gross Unrealized Gains	0	101
Gross Unrealized Losses	(52,534)	(52,313)
Fair Value	623,757	1,060,375
HTM debt securities:
Amortized Cost	532,294	529,548
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(44,587)	(40,997)
Fair Value	487,707	488,551
U.S. government agency and U.S. government-sponsored enterprise debt securities
AFS debt securities:
Amortized Cost	309,956	412,086
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(49,568)	(47,640)
Fair Value	260,388	364,446
HTM debt securities:
Amortized Cost	1,003,094	1,001,836
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(200,199)	(186,904)
Fair Value	802,895	814,932
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	498,281	531,377
Gross Unrealized Gains	113	158
Gross Unrealized Losses	(53,547)	(63,276)
Fair Value	444,847	468,259
HTM debt securities:
Amortized Cost	490,502	493,348
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(90,358)	(88,968)
Fair Value	400,144	404,380
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
AFS debt securities:
Amortized Cost	5,956,800	1,956,927
Gross Unrealized Gains	3,109	380
Gross Unrealized Losses	(241,091)	(229,713)
Fair Value	5,718,818	1,727,594
HTM debt securities:
Amortized Cost	724,039	742,436
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(151,928)	(142,119)
Fair Value	572,111	600,317
Municipal securities
AFS debt securities:
Amortized Cost	295,437	297,283
Gross Unrealized Gains	34	75
Gross Unrealized Losses	(38,908)	(36,342)
Fair Value	256,563	261,016
HTM debt securities:
Amortized Cost	188,321	188,872
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(45,951)	(43,081)
Fair Value	142,370	145,791
Non-agency commercial mortgage-backed securities
AFS debt securities:
Amortized Cost	360,613	409,578
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(39,976)	(42,062)
Fair Value	320,637	367,516
Non-agency residential mortgage-backed securities
AFS debt securities:
Amortized Cost	564,414	643,335
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(89,796)	(89,664)
Fair Value	474,618	553,671
Corporate debt securities
AFS debt securities:
Amortized Cost	653,501	653,501
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(146,371)	(151,076)
Fair Value	507,130	502,425
Foreign government bonds
AFS debt securities:
Amortized Cost	245,523	239,333
Gross Unrealized Gains	1,101	69
Gross Unrealized Losses	(12,900)	(11,528)
Fair Value	233,724	227,874
Asset-backed securities
AFS debt securities:
Amortized Cost	39,061	43,234
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(468)	(934)
Fair Value	38,593	42,300
Collateralized loan obligations (“CLOs”)
AFS debt securities:
Amortized Cost	44,500	617,250
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(47)	(4,389)
Fair Value	$ 44,453	$ 612,861