Securities - Scheduled Contractual Maturities of HTM Debt Securities (Details) $ in Thousands	Jun. 30, 2023 USD ($)
Amortized cost
Within One Year	$ 0
After One Year through Five Years	526,794
After Five Years through Ten Years	376,098
After Ten Years	2,073,041
Total	2,975,933
Fair value
Within One Year	0
After One Year through Five Years	474,137
After Five Years through Ten Years	317,943
After Ten Years	1,648,404
Total	$ 2,440,484
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	1.05%
After Five Years through Ten Years	1.83%
After Ten Years	1.78%
Total	1.66%
U.S. Treasury securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	526,794
After Five Years through Ten Years	0
After Ten Years	0
Total	526,794
Fair value
Within One Year	0
After One Year through Five Years	474,137
After Five Years through Ten Years	0
After Ten Years	0
Total	$ 474,137
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-sponsored enterprises debt securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	0
After Five Years through Ten Years	280,571
After Ten Years	719,844
Total	1,000,415
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	237,713
After Ten Years	560,158
Total	$ 797,871
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	1.92%
After Ten Years	1.89%
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	0
After Five Years through Ten Years	95,527
After Ten Years	1,163,898
Total	1,259,425
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	80,230
After Ten Years	938,796
Total	$ 1,019,026
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	1.56%
After Ten Years	1.68%
Total	1.67%
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	189,299
Total	189,299
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	149,450
Total	$ 149,450
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	1.98%
Total	1.98%