Net Income per Share - Reconciliation of Calculation of Basic and Diluted Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 5,490	$ 3,757	$ 16,117	$ 10,393
Weighted average common shares outstanding - Basic (in shares)	10,743	10,572	10,713	10,543
Plus: Potential dilutive common stock equivalents (in shares)	193	189	197	191
Weighted average common shares outstanding - Diluted (in shares)	10,936	10,761	10,910	10,734
Net income per common share - Basic (in dollars per share)	$ 0.51	$ 0.36	$ 1.50	$ 0.99
Net income per common share - Diluted (in dollars per share)	$ 0.50	$ 0.35	$ 1.48	$ 0.97
Stock options and common stock excluded from the income per share calculation as their effect would have been anti-dilutive (in shares)	40	77	103	70