Stock-Based Compensation (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) $ / shares shares
Employee stock option
Summary of stock option activity - Shares
Options outstanding at December 31, 2015 (in shares)	4,408,000
Granted (in shares)	1,821,000
Exercised (in shares)	(76,000)
Cancelled (in shares)	(73,000)
Expired (in shares)	0
Options outstanding at June 30, 2016 (in shares)	6,080,000
Options exercisable at June 30, 2016 (in shares)	2,227,000
Options vested or expected to vest at June 30, 2016 (in shares)	5,949,000
Summary of stock option activity - Weighted-Average Exercise Price (in dollars per share)
Options outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 28.75
Granted (in dollars per share) | $ / shares	33.85
Exercised (in dollars per share) | $ / shares	21.90
Cancelled (in dollars per share) | $ / shares	38.18
Expired (in dollars per share) | $ / shares	0.00
Options outstanding at the end of the period (in dollars per share) | $ / shares	30.25
Options exercisable at the end of the period (in dollars per share) | $ / shares	15.93
Options vested and expected to vest at the end of the period (in dollars per share) | $ / shares	$ 30.05
Weighted-Average Contractual Life (In Years)
Options outstanding at the end of the period	8 years 113 days
Options exercisable at the end of the period	6 years 314 days
Options vested and expected to vest at the end of the period	8 years 106 days
Aggregate Intrinsic Value
Options outstanding at the end of the period (in dollars) | $	$ 72,281
Options exercisable at the end of the period (in dollars) | $	48,459
Options vested and expected to vest at the end of the period (in dollars) | $	$ 71,598
Restricted stock units (RSUs)
Stock-based Compensation
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Restricted Stock Units Awarded	58,500
Summary of restricted stock units activity
RSUs Outstanding at December 31, 2015 (in shares)	0
Granted (in shares)	59,000
Vested (in shares)	0
Forfeited (in shares)	0
RSUs Outstanding at June 30, 2016 (in shares)	59,000
Summary of stock option activity - Weighted-Average Grant Date Fair Value (in dollars per share)
RSUs outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 33.03
Granted (in dollars per share) | $ / shares	33.03
Exercised (in dollars per share) | $ / shares	0.00
Forfeited (in dollars per share) | $ / shares	0.00
RSUs outstanding at the end of the period (in dollars per share) | $ / shares	$ 0.00