Income Taxes - Summary of Effective Tax Rates Differ from Federal Statutory Rates (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory rate times financial statement income									$ 3,840	$ 4,636	$ 4,086
Effect of:
Meals and entertainment									34	39	39
State income taxes, net of federal tax benefit									1,509	1,608	1,494
Stock option expense and related excess tax benefits									(134)	(419)	(400)
Company owned life insurance									(55)	(314)	(64)
Other, net									(87)	(231)	49
Effect of income tax rate to income before taxes									1,267	683	1,118
Total tax expense	$ 1,513	$ 1,459	$ 972	$ 1,163	$ 1,334	$ 1,238	$ 1,229	$ 1,518	$ 5,107	$ 5,319	$ 5,204