Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net income		$ 661.8	$ 346.2	$ 241.7
Weighted average common shares outstanding (in shares)		74,400,000	73,900,000	74,000,000.0
Dilutive effect of equity awards, based on the treasury stock method (in shares)		1,900,000	1,900,000	1,400,000
Weighted average shares assuming dilution (in shares)		76,300,000	75,800,000	75,400,000
Antidilutive options excluded from computation of diluted net income per share (in shares)		0	0	100,000
Stock repurchase program, shares authorized (in shares)	650,000	650,000	631,000
Shares purchased under share repurchase program (in shares)	0	479,000
Shares purchased under share repurchase program		$ 137.1	$ 115.5	$ 83.1
Shares purchased under share repurchase program, average cost per share (in dollars per share)		$ 286.23