Securities - Scheduled Contractual Maturities of AFS Debt Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Amortized cost
Within One Year	$ 582,092
After One Year through Five Years	628,822
After Five Years through Ten Years	908,682
After Ten Years	11,500,185
Total	13,619,781	$ 11,505,775
Fair value
Within One Year	573,418
After One Year through Five Years	618,819
After Five Years through Ten Years	801,082
After Ten Years	11,218,901
Total	$ 13,212,220
Weighted-Average Yield
Within One Year	1.44%
After One Year through Five Years	2.76%
After Five Years through Ten Years	2.63%
After Ten Years	4.55%
Total	4.21%
U.S. Treasury securities
Amortized cost
Within One Year	$ 440,969
After One Year through Five Years	472,570
After Five Years through Ten Years	96,514
After Ten Years	0
Total	1,010,053	676,300
Fair value
Within One Year	432,148
After One Year through Five Years	465,270
After Five Years through Ten Years	96,495
After Ten Years	0
Total	$ 993,913
Weighted-Average Yield
Within One Year	1.11%
After One Year through Five Years	2.75%
After Five Years through Ten Years	3.84%
After Ten Years	0.00%
Total	2.14%
U.S. government agency and U.S. government-sponsored enterprise debt securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	26,677
After Five Years through Ten Years	203,514
After Ten Years	57,496
Total	287,687	308,220
Fair value
Within One Year	0
After One Year through Five Years	26,256
After Five Years through Ten Years	182,396
After Ten Years	49,002
Total	$ 257,654
Weighted-Average Yield
Within One Year	0.00%
After One Year through Five Years	1.58%
After Five Years through Ten Years	2.07%
After Ten Years	2.16%
Total	2.04%
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	53,961
After Five Years through Ten Years	98,540
After Ten Years	10,391,777
Total	10,544,278
Fair value
Within One Year	0
After One Year through Five Years	52,339
After Five Years through Ten Years	91,020
After Ten Years	10,254,632
Total	$ 10,397,991
Weighted-Average Yield
Within One Year	0.00%
After One Year through Five Years	2.82%
After Five Years through Ten Years	2.83%
After Ten Years	4.79%
Total	4.76%
Municipal securities
Amortized cost
Within One Year	$ 7,300
After One Year through Five Years	19,206
After Five Years through Ten Years	22,614
After Ten Years	228,155
Total	277,275	287,301
Fair value
Within One Year	7,219
After One Year through Five Years	18,679
After Five Years through Ten Years	19,438
After Ten Years	197,766
Total	$ 243,102
Weighted-Average Yield
Within One Year	1.15%
After One Year through Five Years	2.50%
After Five Years through Ten Years	2.40%
After Ten Years	2.26%
Total	2.26%
Non-agency mortgage-backed securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	1,324
After Five Years through Ten Years	0
After Ten Years	665,871
Total	667,195
Fair value
Within One Year	0
After One Year through Five Years	1,320
After Five Years through Ten Years	0
After Ten Years	583,415
Total	$ 584,735
Weighted-Average Yield
Within One Year	0.00%
After One Year through Five Years	3.35%
After Five Years through Ten Years	0.00%
After Ten Years	2.28%
Total	2.28%
Corporate debt securities
Amortized cost
Within One Year	$ 15,158
After One Year through Five Years	26,500
After Five Years through Ten Years	437,500
After Ten Years	75,000
Total	554,158	653,500
Fair value
Within One Year	15,116
After One Year through Five Years	26,204
After Five Years through Ten Years	361,829
After Ten Years	61,832
Total	$ 464,981
Weighted-Average Yield
Within One Year	4.07%
After One Year through Five Years	5.23%
After Five Years through Ten Years	2.38%
After Ten Years	2.09%
Total	2.53%
Foreign government bonds
Amortized cost
Within One Year	$ 118,665
After One Year through Five Years	28,584
After Five Years through Ten Years	50,000
After Ten Years	50,000
Total	247,249	244,803
Fair value
Within One Year	118,935
After One Year through Five Years	28,751
After Five Years through Ten Years	49,904
After Ten Years	40,865
Total	$ 238,455
Weighted-Average Yield
Within One Year	2.31%
After One Year through Five Years	1.81%
After Five Years through Ten Years	4.34%
After Ten Years	1.50%
Total	2.50%
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	31,886
Total	31,886	$ 35,086
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	31,389
Total	$ 31,389
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	4.65%
Total	4.65%