Summary of Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Basic net income (loss)	$ 2,999	$ 647	$ 656	$ 3,086
Diluted net income (loss)	$ 2,999	$ 647	$ 656	$ 3,086
Denominator:
Basic weighted average shares outstanding (in shares)	22,584	22,487	22,577	22,479
Effect of diluted securities (in shares)	341	313	331	306
Diluted weighted average shares outstanding (in shares)	22,925	22,800	22,908	22,785
Basic earnings (loss) per share (in dollars per share)	$ 0.13	$ 0.03	$ 0.03	$ 0.14
Diluted earnings (loss) per share (in dollars per share)	$ 0.13	$ 0.03	$ 0.03	$ 0.14