Investment Securities - Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity, amortized cost, one year or less	$ 1,473
Held-to-maturity, amortized cost, after one through five years	9,159
Held-to-maturity, amortized cost, after five through ten years	387,939
Held-to-maturity, amortized cost, after ten years	2,169,237
Held-to-maturity, amortized cost, securities not due on a single maturity date	1,161,694
Amortized Cost	3,729,502	$ 3,761,094
Held-to-maturity, fair value, one year or less	1,412
Held-to-maturity, fair value, after one through five years	8,877
Held-to-maturity, fair value, after five through ten years	345,785
Held-to-maturity, fair value, after ten years	1,725,082
Held-to-maturity, fair value, securities not due on a single maturity date	1,054,214
Held-to-maturity, fair value, total	3,135,370	3,063,233
Available-for-sale, amortized cost, one year or less	10,418
Available-for-sale, amortized cost, after one through five years	115,387
Available-for-sale, amortized cost, after five through ten years	216,076
Available-for-sale, amortized cost, after ten years	1,028,920
Available-for-sale, amortized cost, securities not due on a single maturity date	2,138,652
Available-for-sale, amortized cost, other securities (no maturity)	256
Amortized Cost	3,509,709	4,331,413
Available-for-sale, fair value, one year or less	10,115
Available-for-sale, fair value, after one through five years	114,069
Available-for-sale, fair value, after five through ten years	190,533
Available-for-sale, fair value, after ten years	896,873
Available-for-sale, fair value, securities not due on a single maturity date	1,940,307
Available-for-sale, fair value, other securities (no maturity)	256
Available-for-sale, fair value, total	$ 3,152,153	$ 3,852,854