Investment Securities - Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity, amortized cost, one year or less	$ 4,519
Held-to-maturity, amortized cost, after one through five years	7,671
Held-to-maturity, amortized cost, after five through ten years	327,461
Held-to-maturity, amortized cost, after ten years	2,233,927
Held-to-maturity, amortized cost, securities not due on a single maturity date	1,214,882
Amortized Cost	3,788,460	$ 1,530,500
Held-to-maturity, fair value, one year or less	4,519
Held-to-maturity, fair value, after one through five years	7,449
Held-to-maturity, fair value, after five through ten years	284,166
Held-to-maturity, fair value, after ten years	1,603,392
Held-to-maturity, fair value, securities not due on a single maturity date	1,084,514
Held-to-maturity, fair value, total	2,984,040	1,517,378
Available-for-sale, amortized cost, one year or less	3,165
Available-for-sale, amortized cost, after one through five years	184,193
Available-for-sale, amortized cost, after five through ten years	268,732
Available-for-sale, amortized cost, after ten years	1,067,671
Available-for-sale, amortized cost, securities not due on a single maturity date	2,959,882
Available-for-sale, amortized cost, other securities (no maturity)	488
Amortized Cost	4,484,131	7,130,861
Available-for-sale, fair value, one year or less	3,142
Available-for-sale, fair value, after one through five years	177,833
Available-for-sale, fair value, after five through ten years	248,862
Available-for-sale, fair value, after ten years	836,869
Available-for-sale, fair value, securities not due on a single maturity date	2,670,348
Available-for-sale, fair value, other securities (no maturity)	489
Available-for-sale, fair value, total	$ 3,937,543	$ 7,113,545