CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
BALANCE at Dec. 31, 2016	$ 9	$ 383,193	$ (342,385)	$ 40,817
BALANCE, Shares at Dec. 31, 2016	89,066,031
Issuance of common stock for stock option exercises		3,084		$ 3,084
Issuance of common stock for stock option exercise, Shares	1,033,121			1,033,121
Vesting of early exercised stock options, Shares	2,477
Issuance of common stock pursuant to the Employee Stock Purchase Plan		4,562		$ 4,562
Issuance of common stock pursuant to the Employee Stock Purchase Plan, Shares	1,676,158
Issuance of common stock pursuant to the Employee Stock-Settled Bonus Plans		8,272		8,272
Issuance of common stock pursuant to the Employee Stock-Settled Bonus Plans, Shares	1,688,097
Shares withheld for net settlement of Employee Stock-Settled Bonus Plans		(3,149)		(3,149)
Shares withheld for net settlement of Employee Stock-Settled Bonus Plans, Shares	(677,547)
Vesting of restricted stock units	$ 1	(1)
Vesting of restricted stock units, Shares	3,260,486
Stock-based compensation		18,496		18,496
Net loss			(48,442)	(48,442)
BALANCE at Sep. 30, 2017	$ 10	$ 414,457	$ (390,827)	$ 23,640
BALANCE, Shares at Sep. 30, 2017	96,048,823