Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - 9 months ended Sep. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at Dec. 31, 2017	$ 152,279	$ 10	$ 436,278	$ (671)		$ (283,338)
Balance, Shares at Dec. 31, 2017		99,157
Vesting of early exercised stock options	213		213
Issuance of common stock pursuant to equity incentive plans, net of taxes	25,490	$ 1	25,558	(69)
Issuance of common stock pursuant to equity incentive plans, net of taxes, Shares		9,501
Issuance of common stock pursuant to exercise of common stock warrants, net, Shares		141
Stock-based compensation expense	21,237		21,237
Cumulative effect change in accounting principle | Accounting Standards Update 2016-16	(40)					(40)
Cumulative effect change in accounting principle | Accounting Standards Update 2014-09	38,339					38,339
Unrealized loss on short-term investments	(7)				$ (7)
Net loss	(15,635)					(15,635)
Balance at Sep. 30, 2018	$ 221,876	$ 11	$ 483,286	$ (740)	$ (7)	$ (260,674)
Balance, Shares at Sep. 30, 2018		108,799