Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	APIC	Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Cumulative-effect of accounting change adopted as of January 1, 2018	$ 5,923			$ 5,923
Beginning Balance at Dec. 31, 2017	$ 313,118	$ 10	$ 664,192	(351,084)
Balance (in shares) at Dec. 31, 2017	100,428,656	100,428,656
Increase (Decrease) in Stockholders' Equity
Net loss	$ (21,928)			(21,928)
Stock-based compensation	29,674		29,674
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes	17,055	$ 0	17,055
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes (in shares)		3,390,692
Ending Balance at Sep. 30, 2018	$ 343,842	$ 10	$ 710,921	$ (367,089)
Balance (in shares) at Sep. 30, 2018	103,819,348	103,819,348