Investment Securities - Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity, amortized cost, one year or less	$ 3,794
Held-to-maturity, amortized cost, after one through five years	7,513
Held-to-maturity, amortized cost, after five through ten years	313,724
Held-to-maturity, amortized cost, after ten years	2,251,319
Held-to-maturity, amortized cost, securities not due on a single maturity date	1,244,713
Amortized Cost	3,821,063	$ 1,530,500
Held-to-maturity, fair value, one year or less	3,813
Held-to-maturity, fair value, after one through five years	7,556
Held-to-maturity, fair value, after five through ten years	290,805
Held-to-maturity, fair value, after ten years	1,790,105
Held-to-maturity, fair value, securities not due on a single maturity date	1,186,683
Held-to-maturity, fair value, total	3,278,962	1,517,378
Available-for-sale, amortized cost, one year or less	4,084
Available-for-sale, amortized cost, after one through five years	171,681
Available-for-sale, amortized cost, after five through ten years	278,500
Available-for-sale, amortized cost, after ten years	1,124,785
Available-for-sale, amortized cost, securities not due on a single maturity date	3,150,519
Available-for-sale, amortized cost, other securities (no maturity)	609
Amortized Cost	4,730,178	7,130,861
Available-for-sale, fair value, one year or less	4,077
Available-for-sale, fair value, after one through five years	167,509
Available-for-sale, fair value, after five through ten years	269,311
Available-for-sale, fair value, after ten years	936,207
Available-for-sale, fair value, securities not due on a single maturity date	2,963,934
Available-for-sale, fair value, other securities (no maturity)	609
Available-for-sale, fair value, total	$ 4,341,647	$ 7,113,545