Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares Underlying Options, Outstanding, Beginning balance	1,896
Number of Shares Underlying Options, Granted	582
Number of Shares Underlying Options, Exercised	(168)
Number of Shares Underlying Options, Forfeited or Cancelled	(73)
Number of Shares Underlying Options, Outstanding, Ending balance	2,237	1,896
Number of Shares Underlying Options, Vested and exercisable	1,022
Weighted-Average Exercise Price Per Share, Outstanding, Beginning balance	$ 3.72
Weighted-Average Exercise Price Per Share, Granted	19.62
Weighted-Average Exercise Price Per Share, Exercised	3.30
Weighted-Average Exercise Price Per Share, Forfeited or Cancelled	5.64
Weighted-Average Exercise Price Per Share, Outstanding, Ending balance	7.84	$ 3.72
Weighted-Average Exercise Price Per Share, Vested and exercisable	$ 2.48
Weighted-Average Remaining Contractual Life (Years), Outstanding	7 years 9 months 15 days	7 years 9 months 7 days
Weighted-Average Remaining Contractual Life (Years), Vested and exercisable	6 years 2 months 27 days
Total Intrinsic Value, Outstanding	$ 66,175	$ 8,666
Total Intrinsic Value, Vested and exercisable	$ 35,704