Securities - Scheduled Contractual Maturities of AFS (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Amortized cost
Within One Year	$ 432,997
After One Year through Five Years	1,017,460
After Five Years through Ten Years	993,979
After Ten Years	4,376,133
Amortized Cost	6,820,569	$ 6,879,225
Fair value
Within One Year	430,800
After One Year through Five Years	935,159
After Five Years through Ten Years	882,803
After Ten Years	3,738,496
Total	$ 5,987,258
Weighted Average Yield
Within One Year	5.04%
After One Year through Five Years	1.88%
After Five Years through Ten Years	4.12%
After Ten Years	3.26%
Total	3.29%
U.S. Treasury securities
Amortized cost
Within One Year	$ 103,679
After One Year through Five Years	676,294
After Five Years through Ten Years	0
After Ten Years	0
Amortized Cost	779,973
Fair value
Within One Year	103,694
After One Year through Five Years	608,012
After Five Years through Ten Years	0
After Ten Years	0
Total	$ 711,706
Weighted Average Yield
Within One Year	4.82%
After One Year through Five Years	1.20%
After Five Years through Ten Years	0.00%
After Ten Years	0.00%
Total	1.68%
U.S. government-sponsored enterprises debt securities
Amortized cost
Within One Year	$ 150,000
After One Year through Five Years	98,133
After Five Years through Ten Years	100,000
After Ten Years	166,461
Amortized Cost	514,594
Fair value
Within One Year	149,305
After One Year through Five Years	93,146
After Five Years through Ten Years	82,433
After Ten Years	135,200
Total	$ 460,084
Weighted Average Yield
Within One Year	4.98%
After One Year through Five Years	3.07%
After Five Years through Ten Years	1.26%
After Ten Years	2.09%
Total	2.96%
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	38,030
After Five Years through Ten Years	151,754
After Ten Years	2,329,981
Amortized Cost	2,519,765
Fair value
Within One Year	0
After One Year through Five Years	35,886
After Five Years through Ten Years	137,852
After Ten Years	2,026,276
Total	$ 2,200,014
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	3.20%
After Five Years through Ten Years	2.71%
After Ten Years	3.48%
Total	3.43%
Municipal securities
Amortized cost
Within One Year	$ 2,301
After One Year through Five Years	37,167
After Five Years through Ten Years	10,777
After Ten Years	253,959
Amortized Cost	304,204
Fair value
Within One Year	2,288
After One Year through Five Years	34,380
After Five Years through Ten Years	9,454
After Ten Years	217,751
Total	$ 263,873
Weighted Average Yield
Within One Year	2.21%
After One Year through Five Years	2.46%
After Five Years through Ten Years	2.73%
After Ten Years	2.24%
Total	2.28%
Non-agency mortgage-backed securities
Amortized cost
Within One Year	$ 102,877
After One Year through Five Years	105,584
After Five Years through Ten Years	12,946
After Ten Years	927,150
Amortized Cost	1,148,557
Fair value
Within One Year	101,397
After One Year through Five Years	101,371
After Five Years through Ten Years	12,525
After Ten Years	777,332
Total	$ 992,625
Weighted Average Yield
Within One Year	6.86%
After One Year through Five Years	4.18%
After Five Years through Ten Years	0.80%
After Ten Years	2.57%
Total	3.08%
Corporate debt securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	349,502
After Ten Years	304,000
Amortized Cost	653,502
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	279,402
After Ten Years	206,348
Total	$ 485,750
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	3.48%
After Ten Years	1.97%
Total	2.78%
Foreign government bonds
Amortized cost
Within One Year	$ 74,140
After One Year through Five Years	62,252
After Five Years through Ten Years	50,000
After Ten Years	50,000
Amortized Cost	236,392
Fair value
Within One Year	74,116
After One Year through Five Years	62,364
After Five Years through Ten Years	49,548
After Ten Years	38,738
Total	$ 224,766
Weighted Average Yield
Within One Year	3.02%
After One Year through Five Years	2.33%
After Five Years through Ten Years	5.46%
After Ten Years	1.50%
Total	3.03%
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	46,332
Amortized Cost	46,332
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	44,875
Total	$ 44,875
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	5.75%
Total	5.75%
Collateralized loan obligations (“CLOs”)
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	319,000
After Ten Years	298,250
Amortized Cost	617,250
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	311,589
After Ten Years	291,976
Total	$ 603,565
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	6.38%
After Ten Years	6.43%
Total	6.40%