Securities - Scheduled Contractual Maturities of AFS (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Amortized cost
Within One Year	$ 558,108
After One Year through Five Years	1,250,437
After Five Years through Ten Years	785,334
After Ten Years	12,461,679
Total	15,055,558	$ 13,619,781
Fair value
Within One Year	552,956
After One Year through Five Years	1,224,510
After Five Years through Ten Years	669,367
After Ten Years	12,134,713
Total	$ 14,581,546
Weighted-average yield
Within One Year	1.32%
After One Year through Five Years	3.22%
After Five Years through Ten Years	2.40%
After Ten Years	4.55%
Total	4.21%
U.S. Treasury securities
Amortized cost
Within One Year	$ 490,491
After One Year through Five Years	890,422
After Five Years through Ten Years	72,033
After Ten Years	0
Total	1,452,946	1,010,053
Fair value
Within One Year	485,561
After One Year through Five Years	875,488
After Five Years through Ten Years	70,292
After Ten Years	0
Total	$ 1,431,341
Weighted-average yield
Within One Year	1.13%
After One Year through Five Years	3.47%
After Five Years through Ten Years	3.78%
After Ten Years	0.00%
Total	2.70%
U.S. government agency and U.S. government-sponsored enterprise debt securities
Amortized cost
Within One Year	$ 1,677
After One Year through Five Years	75,000
After Five Years through Ten Years	153,065
After Ten Years	56,924
Total	286,666	287,687
Fair value
Within One Year	1,659
After One Year through Five Years	69,868
After Five Years through Ten Years	134,895
After Ten Years	47,978
Total	$ 254,400
Weighted-average yield
Within One Year	2.85%
After One Year through Five Years	1.88%
After Five Years through Ten Years	2.15%
After Ten Years	2.15%
Total	2.08%
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities
Amortized cost
Within One Year	$ 81
After One Year through Five Years	56,177
After Five Years through Ten Years	75,152
After Ten Years	11,538,542
Total	11,669,952
Fair value
Within One Year	80
After One Year through Five Years	53,954
After Five Years through Ten Years	68,889
After Ten Years	11,332,302
Total	$ 11,455,225
Weighted-average yield
Within One Year	2.57%
After One Year through Five Years	2.87%
After Five Years through Ten Years	2.82%
After Ten Years	4.74%
Total	4.72%
Municipal securities
Amortized cost
Within One Year	$ 17,453
After One Year through Five Years	6,359
After Five Years through Ten Years	23,584
After Ten Years	224,026
Total	271,422	277,275
Fair value
Within One Year	17,301
After One Year through Five Years	5,986
After Five Years through Ten Years	20,140
After Ten Years	197,261
Total	$ 240,688
Weighted-average yield
Within One Year	2.52%
After One Year through Five Years	1.80%
After Five Years through Ten Years	2.41%
After Ten Years	2.25%
Total	2.28%
Non-agency mortgage-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	617,187
Total	617,187
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	536,241
Total	$ 536,241
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	2.23%
Total	2.23%
Corporate debt securities
Amortized cost
Within One Year	$ 7,375
After One Year through Five Years	62,250
After Five Years through Ten Years	411,500
After Ten Years	25,000
Total	506,125	554,158
Fair value
Within One Year	7,201
After One Year through Five Years	58,683
After Five Years through Ten Years	334,487
After Ten Years	20,931
Total	$ 421,302
Weighted-average yield
Within One Year	6.28%
After One Year through Five Years	4.33%
After Five Years through Ten Years	2.26%
After Ten Years	1.80%
Total	2.55%
Foreign government bonds
Amortized cost
Within One Year	$ 41,031
After One Year through Five Years	160,229
After Five Years through Ten Years	50,000
After Ten Years	0
Total	251,260	$ 247,249
Fair value
Within One Year	41,154
After One Year through Five Years	160,531
After Five Years through Ten Years	40,664
After Ten Years	0
Total	$ 242,349
Weighted-average yield
Within One Year	2.16%
After One Year through Five Years	2.21%
After Five Years through Ten Years	1.75%
After Ten Years	0.00%
Total	2.11%