Securities - Scheduled Contractual Maturities of HTM Debt Securities (Details) $ in Thousands	Jun. 30, 2022 USD ($)
Amortized cost
Within One Year	$ 0
After One Year through Five Years	166,856
After Five Years through Ten Years	654,861
After Ten Years	2,206,585
Total	3,028,302
Fair value
Within One Year	0
After One Year through Five Years	156,200
After Five Years through Ten Years	602,671
After Ten Years	1,897,678
Total	$ 2,656,549
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.90%
After Five Years through Ten Years	1.48%
After Ten Years	1.72%
Total	1.62%
U.S. Treasury securities
Amortized cost
Within One Year	$ 0
After One Year through Five Years	166,856
After Five Years through Ten Years	354,496
After Ten Years	0
Total	521,352
Fair value
Within One Year	0
After One Year through Five Years	156,200
After Five Years through Ten Years	330,321
After Ten Years	0
Total	$ 486,521
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.90%
After Five Years through Ten Years	1.12%
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	213,101
After Ten Years	784,268
Total	997,369
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	193,357
After Ten Years	659,721
Total	$ 853,078
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	2.03%
After Ten Years	1.86%
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	87,264
After Ten Years	1,232,238
Total	1,319,502
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	78,993
After Ten Years	1,081,309
Total	$ 1,160,302
Weighted Average Yield
Within One Year	0.00%
After One Year through Five Years	0.00%
After Five Years through Ten Years	1.60%
After Ten Years	1.59%
Total	1.59%
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	190,079
Total	190,079
Fair value
Within One Year	0
After One Year through Five Years	0
After Five Years through Ten Years	0
After Ten Years	156,648
Total	$ 156,648
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	1.97%
Total	1.97%