Common Stock (Tables)

9 Months Ended

Sep. 30, 2017

Stockholders Equity Note [Abstract]

Schedule of Common Stock Reserved for Issuance

	September 30,	December 31,
	2017	2016
Options outstanding	7,896,734	9,835,992
Unvested restricted stock units outstanding	13,241,111	10,474,975
Unvested early exercised stock options	—	2,471
Shares available for grant under the 2014 Equity Incentive Plan and 2015 Inducement Plan	2,521,805	4,199,415
Shares available for purchase under the Employee Stock Purchase Plan	990,501	575,974
Total	24,650,151	25,088,827