Common Stock and Stockholders' Equity - Stock Plan and Stock Options (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
Stock-based Awards
Vesting period			4 years
Other disclosures
Compensation expense	$ 4,565	$ 1,634	$ 7,662	$ 2,922
Stock options
Aggregate Intrinsic Value
Grant-date fair value of stock options granted during the period	6,400		$ 36,300
Fair value assumptions
Volatility, minimum (as a percent)			45.80%	44.70%
Volatility, maximum (as a percent)			47.70%	46.00%
Expected life (in years)			6 years 1 month 6 days	6 years
Risk-free interest rate, minimum			1.81%	1.24%
Risk-free interest rate, maximum			2.30%	1.91%
Dividend yield (as a percent)			0.00%	0.00%
Weighted-average fair value of the underlying common stock			$ 22.52	$ 5.71
Other disclosures
Compensation expense	4,300	$ 1,600	$ 7,200	$ 2,900
Unrecognized compensation cost	$ 54,700		$ 54,700
Period over which unrecognized compensation cost is expected to be recognized			3 years 3 months 18 days
Stock options | Maximum
Stock-based Awards
Exercisable period (in years)			10 years
2015 Incentive Award Plan
Shares Available for Grant
Balance, beginning of period (in shares)			343,216
Increase in Plan authorized shares			3,676,722
Restricted Stock Units granted (in shares)			(144,618)
Stock options grants (in shares)			(2,979,721)
Stock options forfeited (in shares)			519,361
Balance, end of period (in shares)	1,414,960		1,414,960		343,216
2015 Incentive Award Plan | Stock options
Number of Shares Outstanding
Balance, beginning of period (in shares)			6,839,868
Stock option grants (in shares)			2,979,721
Stock option exercised (in shares)			(479,339)
Stock options forfeited (in shares)			(519,361)
Balance, end of period (in shares)	8,820,889		8,820,889		6,839,868
Vested or expected to vest at end of period (in shares)	8,820,889		8,820,889
Exercisable as of end of period (in shares)	2,166,249		2,166,249
Weighted-Average Exercise Price
Balance, beginning of period (in dollars per share)			$ 11.70
Stock option grants (in dollars per share)			22.52
Stock option exercised (in dollars per share)			9.01
Stock options forfeited (in dollars per share)			16.25
Balance, end of period (in dollars per share)	$ 15.24		15.24		$ 11.70
Vested or expected to vest at end of period (in dollars per share)	15.24		15.24
Exercisable as of end of period (in dollars per share)	$ 8.13		$ 8.13
Weighted-average remaining contractual life in Years
Weighted-average remaining contractual life (in years)			8 years 7 months 24 days		8 years 7 months 21 days
Vested or expected to vest at end of period (in years)			8 years 7 months 24 days
Exercisable as of end of period (in years)			7 years 3 months 29 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 171,676		$ 171,676		$ 36,795
Stock options exercised			8,810
Stock options forfeited			3,377
Vested or expected to vest at end of period	171,676		171,676
Exercisable as of end of period	$ 57,552		$ 57,552