Common Stock - Shares of common stock reserved for issuance (Details) - shares	Mar. 31, 2017	Dec. 31, 2016
Options outstanding	8,778,134	9,835,992
Unvested early exercised stock options	1,534	2,471
Shares available for issuance under the plan	6,306,437	4,199,415
Total	27,318,528	25,088,827
RSUs
Unvested restricted stock outstanding	11,558,974	10,474,975
2014 Employee Stock Purchase Plan | Employees Stock Purchase Plan
Shares available for purchase under Employee Stock Purchase Plan	673,449	575,974
Total	673,449	575,974