Securities - Scheduled Contractual Maturities of AFS (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Amortized cost
Within One Year	$ 185,142
After One Year through Five Years	861,917
After Five Years through Ten Years	771,030
After Ten Years	8,849,204
Amortized Cost	10,667,293	$ 6,916,491
Fair value
Within One Year	183,256
After One Year through Five Years	825,144
After Five Years through Ten Years	697,704
After Ten Years	8,427,773
Total	$ 10,133,877
Weighted Average Yield
Within One Year	3.11%
After One Year through Five Years	1.47%
After Five Years through Ten Years	3.38%
After Ten Years	4.95%
Total	4.52%
U.S. Treasury securities
Amortized cost
Within One Year	$ 59,430
After One Year through Five Years	616,864
After Five Years through Ten Years	0
After Ten Years	0
Amortized Cost	676,294
Fair value
Within One Year	58,770
After One Year through Five Years	582,803
After Five Years through Ten Years	0
After Ten Years	0
Total	$ 641,573
Weighted Average Yield
Within One Year	2.15%
After One Year through Five Years	1.12%
After Five Years through Ten Years	0.00%
After Ten Years	0.00%
Total	1.21%
U.S. government agency and U.S. government-sponsored enterprise debt securities
Amortized cost
Within One Year	$ 17,972
After One Year through Five Years	27,030
After Five Years through Ten Years	176,548
After Ten Years	87,727
Amortized Cost	309,277
Fair value
Within One Year	17,459
After One Year through Five Years	25,738
After Five Years through Ten Years	154,620
After Ten Years	74,631
Total	$ 272,448
Weighted Average Yield
Within One Year	1.06%
After One Year through Five Years	1.13%
After Five Years through Ten Years	1.92%
After Ten Years	2.17%
Total	1.88%
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities
Amortized cost
Within One Year	$ 3,537
After One Year through Five Years	46,592
After Five Years through Ten Years	133,018
After Ten Years	7,327,572
Amortized Cost	7,510,719
Fair value
Within One Year	3,494
After One Year through Five Years	45,121
After Five Years through Ten Years	124,704
After Ten Years	7,139,482
Total	$ 7,312,801
Weighted Average Yield
Within One Year	2.72%
After One Year through Five Years	2.91%
After Five Years through Ten Years	2.80%
After Ten Years	5.49%
Total	5.42%
Municipal securities
Amortized cost
Within One Year	$ 3,140
After One Year through Five Years	32,928
After Five Years through Ten Years	8,116
After Ten Years	247,857
Amortized Cost	292,041
Fair value
Within One Year	3,077
After One Year through Five Years	31,538
After Five Years through Ten Years	7,728
After Ten Years	217,955
Total	$ 260,298
Weighted Average Yield
Within One Year	0.88%
After One Year through Five Years	2.37%
After Five Years through Ten Years	3.38%
After Ten Years	2.23%
Total	2.26%
Non-agency mortgage-backed securities
Amortized cost
Within One Year	$ 74,825
After One Year through Five Years	16,834
After Five Years through Ten Years	9,347
After Ten Years	795,853
Amortized Cost	896,859
Fair value
Within One Year	74,153
After One Year through Five Years	16,669
After Five Years through Ten Years	9,304
After Ten Years	695,714
Total	$ 795,840
Weighted Average Yield
Within One Year	4.44%
After One Year through Five Years	3.60%
After Five Years through Ten Years	6.04%
After Ten Years	2.46%
Total	2.68%
Corporate debt securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	349,501
After Ten Years	304,000
Amortized Cost	653,501
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	307,110
After Ten Years	224,709
Total	$ 531,819
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	3.50%
After Ten Years	1.97%
Total	2.79%
Foreign government bonds
Amortized cost
Within One Year	$ 26,238
After One Year through Five Years	121,669
After Five Years through Ten Years	50,000
After Ten Years	50,000
Amortized Cost	247,907
Fair value
Within One Year	26,303
After One Year through Five Years	123,275
After Five Years through Ten Years	49,744
After Ten Years	39,547
Total	$ 238,869
Weighted Average Yield
Within One Year	3.23%
After One Year through Five Years	2.22%
After Five Years through Ten Years	5.74%
After Ten Years	1.50%
Total	2.90%
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	36,195
Amortized Cost	36,195
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	35,735
Total	$ 35,735
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	6.01%
Total	6.01%
Collateralized loan obligations (“CLOs”)
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	44,500
After Ten Years	0
Amortized Cost	44,500
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	44,494
After Ten Years	0
Total	$ 44,494
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	6.74%
After Ten Years	0.00%
Total	6.74%