Securities - Securities Available-for-sale and Held-to-maturity by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Securities held-to-maturity, amortized cost, due after ten years	$ 50,825
Securities held-to-maturity, fair value, due after ten years	54,538
Securities held-to-maturity, amortized cost	58,739	$ 58,888
Securities held-to-maturity, fair value	63,529	62,112
Securities available for sale, amortized cost, due after one years through five years	45,000
Securities available for sale, fair value, due after one years through five years	43,738
Securities available for sale, amortized cost, due after five years through ten years	138,730
Securities available for sale, fair value, due after five years through ten years	133,201
Securities available for sale, amortized cost, due after ten years	54,578
Securities available for sale, fair value, due after ten years	53,872
Securities available for sale, amortized cost, total other securities	646,112	778,294
Securities available for sale, fair value, total other securities	647,974	772,500
Total Other Securities [Member]
Securities held-to-maturity, amortized cost	50,825
Securities held-to-maturity, fair value	54,538
Securities available for sale, amortized cost, total other securities	238,308
Securities available for sale, fair value, total other securities	230,811
Mutual Fund Debt Securities [Member]
Securities available for sale, amortized cost, total other securities	12,703	12,216
Securities available for sale, fair value, total other securities	12,703	12,216
Collateralized Mortgage Backed Securities [Member]
Securities held-to-maturity, amortized cost	7,914	7,934
Securities held-to-maturity, fair value	8,991	8,114
Securities available for sale, amortized cost, total other securities	395,101	521,600
Securities available for sale, fair value, total other securities	$ 404,460	$ 523,849

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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