Investment Securities - Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity, amortized cost, one year or less	$ 5,333
Held-to-maturity, amortized cost, after one through five years	4,801
Held-to-maturity, amortized cost, after five through ten years	27,081
Held-to-maturity, amortized cost, after ten years	1,422,943
Held-to-maturity, amortized cost, securities not due on a single maturity date	70,342
Amortized Cost	1,530,500	$ 335,946
Held-to-maturity, fair value, one year or less	5,396
Held-to-maturity, fair value, after one through five years	5,023
Held-to-maturity, fair value, after five through ten years	25,874
Held-to-maturity, fair value, after ten years	1,411,936
Held-to-maturity, fair value, securities not due on a single maturity date	69,149
Held-to-maturity, fair value, total	1,517,378	341,925
Available-for-sale, amortized cost, one year or less	7,821
Available-for-sale, amortized cost, after one through five years	61,456
Available-for-sale, amortized cost, after five through ten years	532,085
Available-for-sale, amortized cost, after ten years	2,043,326
Available-for-sale, amortized cost, securities not due on a single maturity date	4,485,547
Available-for-sale, amortized cost, other securities (no maturity)	626
Amortized Cost	7,130,861	3,397,043
Available-for-sale, fair value, one year or less	7,845
Available-for-sale, fair value, after one through five years	61,669
Available-for-sale, fair value, after five through ten years	533,711
Available-for-sale, fair value, after ten years	2,061,081
Available-for-sale, fair value, securities not due on a single maturity date	4,448,615
Available-for-sale, fair value, other securities (no maturity)	624
Available-for-sale, fair value, total	$ 7,113,545	$ 3,473,598