Share-Based Compensation - Stock and Status (Details) - Stock options - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Number of Options
Outstanding at beginning of the period (in shares)			7,680,194
Granted (in shares)			14,603
Exercised (in shares)	(80,650)	(333,049)	(213,439)	(346,549)
Forfeited/canceled (in shares)			(333)
Outstanding at the end of the period (in shares)	7,481,025		7,481,025
Exercisable at the end of the period (in shares)	5,762,448		5,762,448
Unvested at the end of the period (in shares)	1,718,577		1,718,577
Weighted Average Exercise Price
Outstanding at beginning of the period (in dollars per share)			$ 126.27
Granted (in dollars per share)			164.10
Exercised (in dollars per share)			132.38
Forfeited (in dollars per share)			146.03
Outstanding at the end of the period (in dollars per share)	$ 126.17		126.17
Exercisable at the end of the period (in dollars per share)	125.60		125.60
Unvested at the end of the period (in dollars per share)	$ 128.07		$ 128.07
Weighted Average Remaining Contractual Term (in Years)
Outstanding at the end of the period (in Years)			5 years 1 month 6 days
Exercisable at the end of the period (in Years)			4 years 10 months 24 days
Unvested at the end of the period (in Years)			5 years 9 months 18 days
Aggregate Intrinsic Value (in millions)
Outstanding at the end of the period	$ 398.3		$ 398.3
Exercisable at the end of the period	310.1		310.1
Unvested at the end of the period	$ 88.2		$ 88.2
Weighted average grant date fair value of stock options (in dollars per share)			$ 54.63	$ 35.53
Aggregate grant date fair value			$ 0.8	$ 2.1
Total grant date fair value of employee stock options that vested			$ 49.7	$ 72.7