Securities - Scheduled Contractual Maturities of AFS (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Amortized cost
Within One Year	$ 128,731
After One Year through Five Years	899,362
After Five Years through Ten Years	848,386
After Ten Years	5,015,043
Amortized Cost	6,891,522	$ 10,087,179
Fair value
Within One Year	128,401
After One Year through Five Years	850,198
After Five Years through Ten Years	785,477
After Ten Years	4,491,428
Total	$ 6,255,504	9,965,353
Weighted Average Yield
Within One Year	2.14%
After One Year through Five Years	1.95%
After Five Years through Ten Years	2.39%
After Ten Years	2.15%
Total	2.15%
U.S. Treasury securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	576,626
After Five Years through Ten Years	99,694
After Ten Years	0
Amortized Cost	676,320	1,049,238
Fair value
Within One Year	0
After One Year through Five Years	536,698
After Five Years through Ten Years	87,988
After Ten Years	0
Total	$ 624,686	1,032,681
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	1.28%
After Five Years through Ten Years	0.74%
After Ten Years	0.00%
Total	1.20%
U.S. government-sponsored enterprises debt securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	29,193
After Five Years through Ten Years	125,001
After Ten Years	170,269
Amortized Cost	324,463	1,333,984
Fair value
Within One Year	0
After One Year through Five Years	27,700
After Five Years through Ten Years	110,199
After Ten Years	147,346
Total	$ 285,245	1,301,971
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	1.62%
After Five Years through Ten Years	1.16%
After Ten Years	2.09%
Total	1.69%
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	13,289
After Five Years through Ten Years	192,287
After Ten Years	2,505,898
Amortized Cost	2,711,474
Fair value
Within One Year	0
After One Year through Five Years	13,205
After Five Years through Ten Years	182,832
After Ten Years	2,278,035
Total	$ 2,474,072
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	3.11%
After Five Years through Ten Years	2.69%
After Ten Years	2.11%
Total	2.15%
Municipal securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	39,712
After Five Years through Ten Years	6,498
After Ten Years	260,209
Amortized Cost	306,419	519,381
Fair value
Within One Year	0
After One Year through Five Years	37,800
After Five Years through Ten Years	5,758
After Ten Years	223,175
Total	$ 266,733	523,158
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	2.47%
After Five Years through Ten Years	1.79%
After Ten Years	2.23%
Total	2.25%
Non-agency mortgage-backed securities
Amortized cost
Within One Year	$ 10,019
After One Year through Five Years	196,136
After Five Years through Ten Years	40,404
After Ten Years	1,012,653
Amortized Cost	1,259,212
Fair value
Within One Year	9,894
After One Year through Five Years	189,963
After Five Years through Ten Years	39,224
After Ten Years	899,676
Total	$ 1,138,757
Weighted Average Yield
Within One Year	4.47%
After One Year through Five Years	3.56%
After Five Years through Ten Years	1.19%
After Ten Years	2.23%
Total	2.42%
Corporate debt securities
Amortized cost
Within One Year	$ 10,000
After One Year through Five Years	0
After Five Years through Ten Years	334,502
After Ten Years	329,000
Amortized Cost	673,502	657,516
Fair value
Within One Year	9,847
After One Year through Five Years	0
After Five Years through Ten Years	309,395
After Ten Years	240,051
Total	$ 559,293	649,665
Weighted Average Yield
Within One Year	3.26%
After One Year through Five Years	0.00%
After Five Years through Ten Years	3.59%
After Ten Years	1.98%
Total	2.80%
Foreign government bonds
Amortized cost
Within One Year	$ 108,712
After One Year through Five Years	44,406
After Five Years through Ten Years	50,000
After Ten Years	50,000
Amortized Cost	253,118	260,447
Fair value
Within One Year	108,660
After One Year through Five Years	44,832
After Five Years through Ten Years	50,081
After Ten Years	39,424
Total	$ 242,997	257,733
Weighted Average Yield
Within One Year	1.82%
After One Year through Five Years	3.01%
After Five Years through Ten Years	0.55%
After Ten Years	1.50%
Total	1.71%
Asset-backed securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	69,764
Amortized Cost	69,764	74,674
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	67,350
Total	$ 67,350	74,558
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	0.00%
After Ten Years	2.74%
Total	2.74%
Collateralized loan obligations (“CLOs”)
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	617,250
Amortized Cost	617,250	592,250
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	596,371
Total	$ 596,371	$ 589,950
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	0.00%
After Ten Years	2.22%
Total	2.22%