Net Income (Loss) per Share Attributable to Common Stock - Computation of Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Numerator:
Net income (loss)	$ 4,304	$ 1,388	$ (23,762)	$ (22,893)	$ (22,526)
Accretion of redeemable convertible preferred stock	(110,921)	65,082	(135,690)	59,869	(55,502)
Undistributed earnings attributable to participating securities	0	(52,805)	0	(29,397)
Net income (loss) attributable to common stock—basic	(106,617)	13,665	(159,452)	7,579
Net income (loss) attributable to common stock—diluted	$ (106,617)	$ 1,388	$ (159,452)	$ (22,893)
Denominator:
Weighted average shares used to compute net income (loss) per share attributable to common stock—basic	14,913,234	14,340,333	14,840,759	14,288,550
Weighted average shares used to compute net income (loss) per share attributable to common stock—diluted	14,913,234	74,080,026	14,840,759	69,710,552
Net income (loss) per share attributable to common stock - basic (in dollars per share)	$ (7.15)	$ 0.95	$ (10.74)	$ 0.53
Net income (loss) per share attributable to common stock - diluted (in dollars per share)	$ (7.15)	$ 0.02	$ (10.74)	$ (0.33)
Net income (loss) attributable to common stock—basic	$ (106,617)	$ 13,665	$ (159,452)	$ 7,579
Add-back: Accretion due to application of if-converted	110,921	(65,082)	135,690	(59,869)	$ 55,502
Add-back: Undistributed earnings attributable to participating securities due to application of if-converted	0	52,805	0	29,397
Net income (loss) attributable to common stock—diluted	$ (106,617)	$ 1,388	$ (159,452)	$ (22,893)