Investment Securities Available-For-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Contractual maturities of investments in debt securities available-for-sale, Amortized Cost
Due in one year or less	$ 115,555
Due after one year through five years	525,017
Due after five years through ten years	89,368
Due after ten years	580
Mortgage-backed securities	442,748
Total debt securities available-for-sale	1,173,268	$ 1,033,771
Contractual maturities of investments in debt securities available-for-sale, Fair Value
Due in one year or less	116,556
Due after one year through five years	537,183
Due after five years through ten years	89,359
Due after ten years	580
Mortgage-backed securities	453,789
Total debt securities available-for-sale	1,197,467	1,040,583
Accrued interest receivable on investment securities available-for-sale	3,840	4,240
U.S. Treasury and Federal agencies securities
Contractual maturities of investments in debt securities available-for-sale, Amortized Cost
Total debt securities available-for-sale	610,195	524,896
Contractual maturities of investments in debt securities available-for-sale, Fair Value
Total debt securities available-for-sale	619,482	526,964
U.S. States and political subdivisions securities
Contractual maturities of investments in debt securities available-for-sale, Amortized Cost
Total debt securities available-for-sale	78,812	83,566
Contractual maturities of investments in debt securities available-for-sale, Fair Value
Total debt securities available-for-sale	81,127	84,505
Mortgage-backed securities - Federal agencies
Contractual maturities of investments in debt securities available-for-sale, Amortized Cost
Total debt securities available-for-sale	442,748	372,458
Contractual maturities of investments in debt securities available-for-sale, Fair Value
Total debt securities available-for-sale	453,789	375,389
Corporate debt securities
Contractual maturities of investments in debt securities available-for-sale, Amortized Cost
Total debt securities available-for-sale	40,813	52,151
Contractual maturities of investments in debt securities available-for-sale, Fair Value
Total debt securities available-for-sale	42,369	53,025
Foreign government and other securities
Contractual maturities of investments in debt securities available-for-sale, Amortized Cost
Total debt securities available-for-sale	700	700
Contractual maturities of investments in debt securities available-for-sale, Fair Value
Total debt securities available-for-sale	$ 700	$ 700