Consolidated Statements of Stockholders’ Equity - 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
Issuance of stock under employee stock awards and other, net	$ 1	2,016				2,017
Issuance of stock under employee stock awards and other, net (in shares)	1,079
Tax withholdings related to vesting of share-based payments		(3,961)				(3,961)
Stock-based compensation expense		9,969				9,969
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				(35)		(35)
Net loss					(23,190)	(23,190)
Ending balance at Dec. 31, 2018	$ 3	554,403	(35,706)	(52)	(451,961)	$ 66,687
Ending balance (in shares) at Dec. 31, 2018	25,483					25,483
Issuance of stock under employee stock awards and other, net		761				$ 761
Issuance of stock under employee stock awards and other, net (in shares)	800
Tax withholdings related to vesting of share-based payments		(2,661)				(2,661)
Stock-based compensation expense		9,829				9,829
Foreign currency translation adjustment				32		32
Net loss					(26,838)	(26,838)
Ending balance at Dec. 31, 2019	$ 3	$ 562,332	$ (35,706)	$ (20)	$ (478,799)	$ 47,810
Ending balance (in shares) at Dec. 31, 2019	26,283					26,283