Net Income per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Net Income per Share
Net income	$ 9,459	$ 8,418	$ 8,496	$ 5,760	$ 5,171	$ 5,368	$ 26,373	$ 16,299
Weighted average common shares outstanding - Basic	10,372			10,630			10,412	10,768
Plus: Potential dilutive common stock equivalents (in shares)	135			76			134	107
Weighted average common shares outstanding - Diluted (in shares)	10,507			10,706			10,546	10,875
Net income per common share - Basic	$ 0.91			$ 0.54			$ 2.53	$ 1.51
Net income per common share - Diluted	$ 0.90			$ 0.54			$ 2.50	$ 1.50
Stock options and common stock excluded from the income per share calculation as their effect would have been anti-dilutive (in shares)	270			430			234	413