Summary of Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Basic net income (loss)	$ (2,343)	$ 2,439
Diluted net income (loss)	$ (2,343)	$ 2,439
Denominator:
Basic weighted average shares outstanding (in shares)	22,570	22,471
Effect of diluted securities (in shares)		247
Diluted weighted average shares outstanding (in shares)	22,570	22,718
Basic earnings (loss) per share (in dollars per share)	$ (0.10)	$ 0.11
Diluted earnings (loss) per share (in dollars per share)	$ (0.10)	$ 0.11