Securities - Scheduled Contractual Maturities of AFS (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Amortized cost
Within One Year	$ 207,263
After One Year through Five Years	958,665
After Five Years through Ten Years	743,510
After Ten Years	7,222,515
Amortized Cost	9,131,953	$ 6,916,491
Fair value
Within One Year	205,152
After One Year through Five Years	897,162
After Five Years through Ten Years	653,911
After Ten Years	6,644,243
Total	$ 8,400,468
Weighted Average Yield
Within One Year	3.55%
After One Year through Five Years	1.72%
After Five Years through Ten Years	3.51%
After Ten Years	4.67%
Total	4.24%
U.S. Treasury securities
Amortized cost
Within One Year	$ 34,901
After One Year through Five Years	641,389
After Five Years through Ten Years	0
After Ten Years	0
Amortized Cost	676,290
Fair value
Within One Year	33,920
After One Year through Five Years	587,174
After Five Years through Ten Years	0
After Ten Years	0
Total	$ 621,094
Weighted Average Yield
Within One Year	1.83%
After One Year through Five Years	1.17%
After Five Years through Ten Years	0.00%
After Ten Years	0.00%
Total	1.20%
U.S. government-sponsored enterprises debt securities
Amortized cost
Within One Year	$ 51,238
After One Year through Five Years	94,159
After Five Years through Ten Years	127,833
After Ten Years	137,446
Amortized Cost	410,676
Fair value
Within One Year	51,163
After One Year through Five Years	90,935
After Five Years through Ten Years	106,727
After Ten Years	111,977
Total	$ 360,802
Weighted Average Yield
Within One Year	4.94%
After One Year through Five Years	3.16%
After Five Years through Ten Years	1.60%
After Ten Years	2.33%
Total	2.62%
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities
Amortized cost
Within One Year	$ 3,219
After One Year through Five Years	36,135
After Five Years through Ten Years	137,555
After Ten Years	5,565,799
Amortized Cost	5,742,708
Fair value
Within One Year	3,130
After One Year through Five Years	34,513
After Five Years through Ten Years	125,890
After Ten Years	5,284,485
Total	$ 5,448,018
Weighted Average Yield
Within One Year	2.68%
After One Year through Five Years	3.15%
After Five Years through Ten Years	2.73%
After Ten Years	5.32%
Total	5.24%
Municipal securities
Amortized cost
Within One Year	$ 2,240
After One Year through Five Years	34,998
After Five Years through Ten Years	9,621
After Ten Years	249,501
Amortized Cost	296,360
Fair value
Within One Year	2,219
After One Year through Five Years	32,747
After Five Years through Ten Years	8,885
After Ten Years	214,644
Total	$ 258,495
Weighted Average Yield
Within One Year	3.39%
After One Year through Five Years	2.23%
After Five Years through Ten Years	3.22%
After Ten Years	2.23%
Total	2.27%
Non-agency mortgage-backed securities
Amortized cost
Within One Year	$ 82,941
After One Year through Five Years	46,116
After Five Years through Ten Years	0
After Ten Years	854,482
Amortized Cost	983,539
Fair value
Within One Year	82,055
After One Year through Five Years	45,322
After Five Years through Ten Years	0
After Ten Years	726,276
Total	$ 853,653
Weighted Average Yield
Within One Year	3.67%
After One Year through Five Years	3.70%
After Five Years through Ten Years	0.00%
After Ten Years	2.54%
Total	2.69%
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	294,845
After Ten Years	207,802
Total	$ 502,647
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	$ 32,724
After One Year through Five Years	105,868
After Five Years through Ten Years	50,000
After Ten Years	50,000
Amortized Cost	238,592
Fair value
Within One Year	32,665
After One Year through Five Years	106,471
After Five Years through Ten Years	49,640
After Ten Years	38,420
Total	$ 227,196
Weighted Average Yield
Within One Year	3.01%
After One Year through Five Years	2.28%
After Five Years through Ten Years	5.72%
After Ten Years	1.50%
Total	2.94%
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	41,287
Amortized Cost	41,287
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	40,712
Total	$ 40,712
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	6.06%
Total	6.06%
Collateralized loan obligations (“CLOs”)
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	69,000
After Ten Years	20,000
Amortized Cost	89,000
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	67,924
After Ten Years	19,927
Total	$ 87,851
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	7.10%
After Ten Years	6.84%
Total	7.04%