Securities - Scheduled Contractual Maturities of AFS (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Amortized cost
Within One Year	$ 178,805
After One Year through Five Years	851,440
After Five Years through Ten Years	840,795
After Ten Years	4,900,314
Amortized Cost	6,771,354	$ 10,087,179
Fair value
Within One Year	178,622
After One Year through Five Years	777,836
After Five Years through Ten Years	745,302
After Ten Years	4,204,330
Total	$ 5,906,090	9,965,353
Weighted Average Yield
Within One Year	2.69%
After One Year through Five Years	1.96%
After Five Years through Ten Years	2.56%
After Ten Years	2.69%
Total	2.58%
U.S. Treasury securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	576,605
After Five Years through Ten Years	99,707
After Ten Years	0
Amortized Cost	676,312	1,049,238
Fair value
Within One Year	0
After One Year through Five Years	516,595
After Five Years through Ten Years	84,082
After Ten Years	0
Total	$ 600,677	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	24,775
After Five Years through Ten Years	125,000
After Ten Years	169,295
Amortized Cost	319,070	1,333,984
Fair value
Within One Year	0
After One Year through Five Years	22,787
After Five Years through Ten Years	102,540
After Ten Years	135,097
Total	$ 260,424	1,301,971
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	1.47%
After Five Years through Ten Years	1.16%
After Ten Years	2.10%
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	24,417
After Five Years through Ten Years	173,899
After Ten Years	2,440,817
Amortized Cost	2,639,133
Fair value
Within One Year	0
After One Year through Five Years	23,529
After Five Years through Ten Years	157,827
After Ten Years	2,133,958
Total	$ 2,315,314
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	3.26%
After Five Years through Ten Years	2.71%
After Ten Years	2.70%
Total	2.71%
Municipal securities
Amortized cost
Within One Year	$ 1,511
After One Year through Five Years	38,079
After Five Years through Ten Years	6,855
After Ten Years	260,639
Amortized Cost	307,084	519,381
Fair value
Within One Year	1,510
After One Year through Five Years	35,025
After Five Years through Ten Years	5,753
After Ten Years	207,214
Total	$ 249,502	523,158
Weighted Average Yield
Within One Year	3.13%
After One Year through Five Years	2.44%
After Five Years through Ten Years	1.85%
After Ten Years	2.24%
Total	2.26%
Non-agency mortgage-backed securities
Amortized cost
Within One Year	$ 28,574
After One Year through Five Years	187,564
After Five Years through Ten Years	25,832
After Ten Years	991,520
Amortized Cost	1,233,490
Fair value
Within One Year	28,195
After One Year through Five Years	179,900
After Five Years through Ten Years	24,897
After Ten Years	836,521
Total	$ 1,069,513
Weighted Average Yield
Within One Year	4.84%
After One Year through Five Years	3.87%
After Five Years through Ten Years	0.84%
After Ten Years	2.37%
Total	2.62%
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	9,857
After One Year through Five Years	0
After Five Years through Ten Years	296,184
After Ten Years	223,524
Total	$ 529,565	649,665
Weighted Average Yield
Within One Year	3.95%
After One Year through Five Years	0.00%
After Five Years through Ten Years	3.59%
After Ten Years	1.98%
Total	2.81%
Foreign government bonds
Amortized cost
Within One Year	$ 138,720
After One Year through Five Years	0
After Five Years through Ten Years	50,000
After Ten Years	50,000
Amortized Cost	238,720	260,447
Fair value
Within One Year	139,060
After One Year through Five Years	0
After Five Years through Ten Years	49,851
After Ten Years	36,899
Total	$ 225,810	257,733
Weighted Average Yield
Within One Year	2.15%
After One Year through Five Years	0.00%
After Five Years through Ten Years	2.66%
After Ten Years	1.50%
Total	2.12%
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	66,793
Amortized Cost	66,793	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	64,870
Total	$ 64,870	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	4.15%
Total	4.15%
Collateralized loan obligations (“CLOs”)
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	25,000
After Ten Years	592,250
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	24,168
After Ten Years	566,247
Total	$ 590,415	$ 589,950
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	3.66%
After Ten Years	3.86%
Total	3.85%