Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - 6 months ended Jun. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	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	173		173
Issuance of common stock pursuant to equity incentive plans, net of taxes	17,384	$ 1	17,435	(52)
Issuance of common stock pursuant to equity incentive plans, net of taxes, Shares		5,763
Issuance of common stock pursuant to exercise of common stock warrants, net, Shares		141
Stock-based compensation expense	9,738		9,738
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
Net loss	(6,108)				(6,108)
Balance at Jun. 30, 2018	$ 211,765	$ 11	$ 463,624	$ (723)	$ (251,147)
Balance, Shares at Jun. 30, 2018		105,061