Securities - Scheduled Contractual Maturities of HTM Debt Securities (Details) $ in Thousands	Mar. 31, 2026 USD ($)
Amortized cost
Within One Year	$ 74,402
After One Year through Five Years	653,436
After Five Years through Ten Years	1,010,532
After Ten Years	1,120,608
Total	2,858,978
Fair value
Within One Year	72,898
After One Year through Five Years	623,357
After Five Years through Ten Years	854,915
After Ten Years	901,833
Total	$ 2,453,003
Weighted Average Yield
Within One Year	0.83%
After One Year through Five Years	1.17%
After Five Years through Ten Years	1.94%
After Ten Years	1.75%
Total	1.66%
U.S. Treasury securities
Amortized cost
Within One Year	$ 74,402
After One Year through Five Years	467,657
After Five Years through Ten Years	0
After Ten Years	0
Total	542,059
Fair value
Within One Year	72,898
After One Year through Five Years	453,150
After Five Years through Ten Years	0
After Ten Years	0
Total	$ 526,048
Weighted Average Yield
Within One Year	0.83%
After One Year through Five Years	1.08%
After Five Years through Ten Years	0.00%
After Ten Years	0.00%
Total	1.05%
U.S. government agency and U.S. government-sponsored enterprise debt securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	129,956
After Five Years through Ten Years	812,191
After Ten Years	65,790
Total	1,007,937
Fair value
Within One Year	0
After One Year through Five Years	118,920
After Five Years through Ten Years	683,742
After Ten Years	52,799
Total	$ 855,461
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	1.37%
After Five Years through Ten Years	1.96%
After Ten Years	2.12%
Total	1.90%
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	55,823
After Five Years through Ten Years	184,457
After Ten Years	883,852
Total	1,124,132
Fair value
Within One Year	0
After One Year through Five Years	51,287
After Five Years through Ten Years	159,382
After Ten Years	717,435
Total	$ 928,104
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	1.51%
After Five Years through Ten Years	1.81%
After Ten Years	1.67%
Total	1.69%
Municipal securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	13,884
After Ten Years	170,966
Total	184,850
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	11,791
After Ten Years	131,599
Total	$ 143,390
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	2.35%
After Ten Years	1.99%
Total	2.02%