Stock-Based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Weighted-average price per share
Allocated Share-based Compensation Expense	$ 23,508	$ 11,685	$ 41,909	$ 21,146
Outstanding stock options
Shares
Outstanding at the beginning of the period (in shares)			6,978,621
Granted (in shares)			661,657
Exercised (in shares)			(373,078)
Cancelled (in shares)			(62,837)
Outstanding at the end of the period (in shares)	7,204,363		7,204,363
Vested at the end of the period (in shares)			3,779,553
Weighted-average price per share
Outstanding at the beginning of the period (in dollars per share)			$ 40.65
Granted (in dollars per share)			162.65
Exercised (in dollars per share)			43.65
Cancelled (in dollars per share)			50.38
Outstanding at the end of the period (in dollars per share)	$ 51.62		51.62
Vested at the end of the period (in dollars per share)	$ 28.34		$ 28.34
Total unrecognized compensation cost related to unvested stock options (in dollars)	$ 142,600		$ 142,600
Weighted average period over which unrecognized compensation costs are expected to be recognized	2 years 6 months