Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 2,227	$ (20,947)	$ (43,230)
Other comprehensive income (loss)
Foreign currency translation adjustments	99	(276)	(153)
Comprehensive income (loss) attributable to common stockholders	$ 2,326	$ (21,223)	$ (43,383)