Investment Securities - Scheduled Maturities of Investment Securities Available-for-Sale and Held-to-Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Available-for-sale, maturing within one year, amortized cost	$ 81
Available-for-sale, maturing after one to five years, amortized cost	27,551
Available-for-sale, maturing after five to ten years, amortized cost	62,218
Available-for-sale, maturing after ten years, amortized cost	26,191
Available-for-sale, amortized cost	116,041	$ 83,289
Available-for-sale, maturing within one year, estimated fair value	82
Available-for-sale, maturing after one to five years, estimated fair value	27,747
Available-for-sale, maturing after five to ten years, estimated fair value	63,275
Available-for-sale, maturing after ten years, estimated fair value	26,456
Available-for-sale, amortized cost	117,560	84,993
Held-to-maturity, maturing within one year, amortized cost	401
Held-to-maturity, maturing after five to ten years, amortized cost	2,052
Held-to-maturity, maturing after ten years, amortized cost	1,454
Held-to-maturity, amortized cost	3,907	6,429
Held-to-maturity, maturing within one year, estimated fair value	404
Held-to-maturity, maturity after five to ten years, estimated fair value	2,100
Held-to-maturity, maturing after ten years, estimated fair value	1,488
Held-to-maturity, amortized cost	$ 3,992	$ 6,559