Condensed Consolidated Statements of Stockholders' Equity - 9 months ended Sep. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional paid-in capital	Treasury stock	Accumulated other comprehensive income (loss)	Accumulated deficit	Total
Beginning balance at Dec. 31, 2017	$ 2	$ 523,012	$ (35,706)	$ (17)	$ (428,771)	$ 58,520
Beginning balance (in shares) at Dec. 31, 2017	21,031					21,031
Issuance of stock under employee stock awards and other		1,469				$ 1,469
Issuance of stock under employee stock awards and other (in shares)	861
Tax withholdings related to vesting of share-based payments		(3,183)				(3,183)
Stock-based compensation expense		7,787				7,787
Issuance of common stock in connection with follow-on public offering, net of offering costs		23,367				23,367
Issuance of common stock in connection with follow-on public offering, net of offering costs (in shares)	3,373
Foreign currency translation adjustment				1		1
Net loss					(18,253)	(18,253)
Ending balance at Sep. 30, 2018	$ 2	$ 552,452	$ (35,706)	$ (16)	$ (447,024)	$ 69,708
Ending balance (in shares) at Sep. 30, 2018	25,265					25,265