CONSOLIDATED STATEMENT OF EQUITY - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Capital in Excess of Par Value	Treasury Stock	Retained earnings	Retained earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated other comprehensive loss
Balance (in shares) at Dec. 31, 2017			75,200,000		1,300,000
Beginning balance at Dec. 31, 2017	$ 1,279.9		$ 18.8	$ 309.3	$ (109.1)	$ 1,178.2		$ (117.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	206.9					206.9
Activity related to stock-based compensation (in shares)			100,000		(900,000)
Activity related to stock-based compensation	48.9			(27.3)	$ 76.2
Shares purchased under share repurchase program (in shares)					800,000
Shares purchased under share repurchase program	$ (70.8)				$ (70.8)
Dividends declared per share (in dollars per share)	$ 0.58
Dividends declared	$ (43.1)					(43.1)
Other comprehensive income, net of tax	(36.9)							(36.9)
Balance (in shares) at Dec. 31, 2018			75,300,000		1,200,000
Ending balance at Dec. 31, 2018	$ 1,396.3	$ 11.4	$ 18.8	282.0	$ (103.7)	1,353.4	$ 11.4	(154.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Net income	$ 241.7					241.7
Activity related to stock-based compensation (in shares)					(800,000)
Activity related to stock-based compensation	54.5			(11.1)	$ 65.6
Shares purchased under share repurchase program (in shares)					800,000
Shares purchased under share repurchase program	(83.1)				$ (83.1)
Purchase of investment in affiliated companies	$ 4.9			1.8	$ 3.1
Dividends declared per share (in dollars per share)	$ 0.62
Dividends declared	$ (45.7)					(45.7)
Other comprehensive income, net of tax	4.6							4.6
Balance (in shares) at Dec. 31, 2019			75,300,000		1,200,000
Ending balance at Dec. 31, 2019	1,573.2	$ (0.1)	$ 18.8	272.7	$ (118.1)	1,549.4	$ (0.1)	(149.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	346.2					346.2
Activity related to stock-based compensation (in shares)					(700,000)
Activity related to stock-based compensation	$ 60.5			(5.4)	$ 65.9
Shares purchased under share repurchase program (in shares)	761,500				800,000
Shares purchased under share repurchase program	$ (115.5)				$ (115.5)
Dividends declared per share (in dollars per share)	$ 0.66
Dividends declared	$ (48.8)					(48.8)
Other comprehensive income, net of tax	39.0							39.0
Balance (in shares) at Dec. 31, 2020			75,300,000		1,300,000
Ending balance at Dec. 31, 2020	$ 1,854.5		$ 18.8	$ 267.3	$ (167.7)	$ 1,846.7		$ (110.6)