Share-Based Compensation - Stock Options Activity (Details) - Stock Option - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Shares
Outstanding at January 1, 2015 (in shares)	2,266,433
Granted (in shares)	570,250
Exercised (in shares)	(675,525)
Forfeited (in shares)	(173,212)
Outstanding at December 31, 2016 (in shares)	1,987,946	2,266,433
Vested and expected to vest at December 31, 2016 (in shares)	1,884,401
Exercisable at December 31, 2016 (in shares)	945,265
Weighted Average Price
Outstanding at January 1, 2015 (in dollars per share)	$ 54.05
Granted (in dollars per share)	75.35
Exercised (in dollars per share)	44.44
Forfeited (in dollars per share)	72.30
Outstanding at December 31, 2016 (in dollars per share)	61.83	$ 54.05
Vested and expected to vest at December 31, 2016 (in dollars per share)	61.06
Exercisable at December 31, 2016 (in dollars per share)	$ 48.53
Weighted-Average Remaining Contractual Term
Weighted-Average Remaining Contractual Term	6 years 10 months 2 days	6 years 6 months 29 days
Vested and expected to vest at December 31, 2016	6 years 8 months 27 days
Exercisable at December 31, 2016	5 years 2 months 1 day
Aggregate Intrinsic Value
Outstanding at January 1, 2015	$ 51,918,028
Outstanding at December 31, 2016	56,144,876	$ 51,918,028
Vested and expected to vest at December 31, 2016	54,671,036
Exercisable at December 31, 2016	$ 39,252,480