Net Income (Loss) Per Share - Computation Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net Income (Loss) Per Share
Net loss	$ (10,018)	$ (11,909)
Weighted average common shares outstanding - basic and diluted (in shares)	19,942	20,213
Net loss per share - basic and diluted (in dollars per share)	$ (0.50)	$ (0.59)