Summary of Significant Accounting Policies - Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Apr. 30, 2021
Anti-dilutive securities
Common stock, authorized shares	30,000,000	30,000,000	15,000,000	30,000,000
Net income for basic and diluted income per common share	$ 45,429	$ 37,045	$ 28,223
Weighted-average shares for basic income per common share (in shares)	5,671,960	5,656,367	5,629,425
Effect of dilutive securities:
Employee and director stock options (in shares)	8,449	11,992	10,438
Adjusted weighted-average shares and assumed exercises for diluted income per common share (in shares)	5,680,409	5,668,359	5,639,863
Basic net income per common share (in dollars per share)	$ 8.01	$ 6.55	$ 5.01
Diluted net income per common share (in dollars per share)	8.00	6.54	5.00
Cash dividends per share of common stock (in dollars per share)	$ 0.80	$ 0.64	$ 0.64
Options
Effect of dilutive securities:
Anti-dilutive shares of common stock excluded from the calculation of dilutive securities	16,125	600	5,550