Investment Securities - Scheduled Maturities of Investment Securities Available-for-Sale and Held-to-Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Available-for-sale, maturing within one year, amortized cost	$ 11,324
Available-for-sale, maturing after one to five years, amortized cost	4,216
Available-for-sale, maturing after five to ten years, amortized cost	39,030
Available-for-sale, maturing after ten years, amortized cost	28,719
Available-for-sale, amortized cost	83,289	$ 94,071
Available-for-sale, maturing within one year, estimated fair value	11,330
Available-for-sale, maturing after one to five years, estimated fair value	4,372
Available-for-sale, maturing after five to ten years, estimated fair value	40,211
Available-for-sale, maturing after ten years, estimated fair value	29,080
Available-for-sale, amortized cost	84,993	94,016
Held-to-maturity, maturing after one to five years, amortized cost	763
Held-to-maturity, maturing after five to ten years, amortized cost	2,716
Held-to-maturity, maturing after ten years, amortized cost	2,950
Held-to-maturity, amortized cost	6,429	14,340
Held-to-maturity, maturing after one to five years, estimated fair value	777
Held-to-maturity, maturity after five to ten years, estimated fair value	2,770
Held-to-maturity, maturing after ten years, estimated fair value	3,012
Held-to-maturity, amortized cost	$ 6,559	$ 14,306