Equity-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Options (in shares):
Options outstanding, beginning (in shares)	4,457,996
Granted (in shares)	1,021,398
Forfeitures/Expired (in shares)	(63,372)
Exercised (in shares)	(935,250)
Options outstanding, ending (in shares)	4,480,772	4,457,996
Options Weighted Average Exercise Price (in dollars per share):
Options outstanding, beginning weighted-average exercise price (in dollars per share)	$ 37.41
Grants, weighted average exercise price (in dollars per share)	73.85
Forfeitures and Expirations, weighted average exercise price (in dollars per share)	59.85
Exercises, weighted average exercise price (in dollars per share)	30.59
Options outstanding, ending weighted-average exercise price (in dollars per share)	$ 46.82	$ 37.41
Options, outstanding, weighted average remaining contractual term	7 years 14 days
Options, outstanding intrinsic value	$ 153.5
Options, exercisable (in shares)	2,423,693
Options, exercisable, weighted average exercise price (in dollars per share)	$ 32.67
Options, exercisable, weighted average remaining contractual term (years)	5 years 9 months 14 days
Options, exercisable, Intrinsic Value	$ 117.3
Options, vested and expected to vest, Outstanding (in shares)	2,031,401
Options, vested and expected to vest, weighted average exercise price (in dollars per share)	$ 63.43
Options, vested and expected to vest, outstanding, weighted average remaining contractual term (in years)	8 years 6 months 7 days
Options, vested and expected to vest, aggregate intrinsic value	$ 35.9
Total intrinsic value of stock options exercised	$ 47.0	$ 17.0	$ 7.0