Securities - Scheduled Contractual Maturities of HTM Debt Securities (Details) $ in Thousands	Mar. 31, 2025 USD ($)
Amortized cost
Within One Year	$ 0
After One Year through Five Years	554,958
After Five Years through Ten Years	499,299
After Ten Years	1,851,084
Total	2,905,341
Fair value
Within One Year	0
After One Year through Five Years	525,544
After Five Years through Ten Years	434,320
After Ten Years	1,475,428
Total	$ 2,435,292
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	1.07%
After Five Years through Ten Years	1.83%
After Ten Years	1.80%
Total	1.66%
U.S. Treasury securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	536,459
After Five Years through Ten Years	0
After Ten Years	0
Total	536,459
Fair value
Within One Year	0
After One Year through Five Years	508,613
After Five Years through Ten Years	0
After Ten Years	0
Total	$ 508,613
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	1.05%
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	0
After Five Years through Ten Years	372,206
After Ten Years	633,141
Total	1,005,347
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	325,760
After Ten Years	505,596
Total	$ 831,356
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	1.89%
After Ten Years	1.90%
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	18,499
After Five Years through Ten Years	127,093
After Ten Years	1,030,723
Total	1,176,315
Fair value
Within One Year	0
After One Year through Five Years	16,931
After Five Years through Ten Years	108,560
After Ten Years	831,159
Total	$ 956,650
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	1.67%
After Five Years through Ten Years	1.66%
After Ten Years	1.69%
Total	1.69%
Municipal securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	187,220
Total	187,220
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	138,673
Total	$ 138,673
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	2.01%
Total	2.01%