Share-based Compensation - Stock Options Activity Rollforward (Details) - Stock Options $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares
Number of Shares
Outstanding at beginning of period (shares) | shares	630
Granted (shares) | shares	110
Exercised (shares) | shares	(310)
Forfeited / Cancelled (shares) | shares	(70)
Outstanding at end of period (shares) | shares	360
Vested and expected to vest (shares) | shares	360
Exercisable at end of year (shares) | shares	150
Weighted-average Exercise Price
Outstanding at beginning of period (usd per share) | $ / shares	$ 46.01
Granted (usd per share) | $ / shares	68.80
Exercised (usd per share) | $ / shares	35.66
Forfeited / Cancelled (usd per share) | $ / shares	59.76
Outstanding at end of period (usd per share) | $ / shares	57.95
Vested and expected to vest at end of year (usd per share) | $ / shares	57.67
Exercisable at end of year (usd per share) | $ / shares	$ 56.51
Outstanding at end of year, aggregate intrinsic value | $	$ 22.6
Vested and expected to vest at end of year, aggregate intrinsic value | $	9.3
Exercisable at end of year, aggregate intrinsic value | $	$ 22.1
Outstanding at end of year, weighted average contractual term	6 years 1 month 6 days
Vested and expected to vest at end of year, weighted average contractual term	6 years
Exercisable at end of year, weighted average contractual term	4 years 6 months