Securities - Scheduled Contractual Maturities of AFS (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Amortized cost
Within One Year	$ 545,806
After One Year through Five Years	1,069,602
After Five Years through Ten Years	1,003,292
After Ten Years	4,453,540
Amortized Cost	7,072,240	$ 6,879,225
Fair value
Within One Year	544,573
After One Year through Five Years	996,090
After Five Years through Ten Years	908,047
After Ten Years	3,852,158
Total	$ 6,300,868
Weighted Average Yield
Within One Year	4.80%
After One Year through Five Years	2.11%
After Five Years through Ten Years	3.93%
After Ten Years	3.19%
Total	3.25%
U.S. Treasury securities
Amortized cost
Within One Year	$ 300,316
After One Year through Five Years	676,299
After Five Years through Ten Years	0
After Ten Years	0
Amortized Cost	976,615
Fair value
Within One Year	300,302
After One Year through Five Years	616,680
After Five Years through Ten Years	0
After Ten Years	0
Total	$ 916,982
Weighted Average Yield
Within One Year	4.57%
After One Year through Five Years	1.20%
After Five Years through Ten Years	0.00%
After Ten Years	0.00%
Total	2.24%
U.S. government-sponsored enterprises debt securities
Amortized cost
Within One Year	$ 100,000
After One Year through Five Years	148,135
After Five Years through Ten Years	100,000
After Ten Years	167,504
Amortized Cost	515,639
Fair value
Within One Year	99,798
After One Year through Five Years	143,681
After Five Years through Ten Years	83,478
After Ten Years	136,903
Total	$ 463,860
Weighted Average Yield
Within One Year	4.97%
After One Year through Five Years	3.72%
After Five Years through Ten Years	1.26%
After Ten Years	2.10%
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	31,502
After Five Years through Ten Years	154,131
After Ten Years	2,376,249
Amortized Cost	2,561,882
Fair value
Within One Year	0
After One Year through Five Years	30,182
After Five Years through Ten Years	141,815
After Ten Years	2,097,200
Total	$ 2,269,197
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	3.22%
After Five Years through Ten Years	2.67%
After Ten Years	3.39%
Total	3.34%
Municipal securities
Amortized cost
Within One Year	$ 2,304
After One Year through Five Years	37,282
After Five Years through Ten Years	10,778
After Ten Years	254,761
Amortized Cost	305,125
Fair value
Within One Year	2,287
After One Year through Five Years	34,889
After Five Years through Ten Years	9,610
After Ten Years	219,229
Total	$ 266,015
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	$ 71,090
After One Year through Five Years	139,963
After Five Years through Ten Years	19,881
After Ten Years	954,838
Amortized Cost	1,185,772
Fair value
Within One Year	70,089
After One Year through Five Years	134,268
After Five Years through Ten Years	19,290
After Ten Years	811,485
Total	$ 1,035,132
Weighted Average Yield
Within One Year	7.23%
After One Year through Five Years	4.42%
After Five Years through Ten Years	0.84%
After Ten Years	2.61%
Total	3.07%
Corporate debt securities
Amortized cost
Within One Year	$ 10,000
After One Year through Five Years	0
After Five Years through Ten Years	349,502
After Ten Years	304,000
Amortized Cost	663,502
Fair value
Within One Year	9,817
After One Year through Five Years	0
After Five Years through Ten Years	294,170
After Ten Years	212,266
Total	$ 516,253
Weighted Average Yield
Within One Year	3.49%
After One Year through Five Years	0.00%
After Five Years through Ten Years	3.48%
After Ten Years	1.97%
Total	2.79%
Foreign government bonds
Amortized cost
Within One Year	$ 62,096
After One Year through Five Years	36,421
After Five Years through Ten Years	50,000
After Ten Years	50,000
Amortized Cost	198,517
Fair value
Within One Year	62,280
After One Year through Five Years	36,390
After Five Years through Ten Years	49,530
After Ten Years	37,683
Total	$ 185,883
Weighted Average Yield
Within One Year	3.19%
After One Year through Five Years	2.35%
After Five Years through Ten Years	4.94%
After Ten Years	1.50%
Total	3.05%
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	47,938
Amortized Cost	47,938
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	46,307
Total	$ 46,307
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	5.59%
Total	5.59%
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	310,154
After Ten Years	291,085
Total	$ 601,239
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	5.93%
After Ten Years	5.99%
Total	5.96%