CONDENSED CONSOLIDATED STATEMENT OF EQUITY (UNAUDITED) - 9 months ended Sep. 30, 2018 - USD ($) $ in Millions	Total	Common Stock [Member]	Capital in Excess of Par Value [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balance at Dec. 31, 2017	$ 1,279.9	$ 18.8	$ 309.3	$ (109.1)	$ 1,178.2	$ (117.3)
Balance (in shares) at Dec. 31, 2017		75,200,000		1,300,000
Increase (Decrease) in Equity [Roll Forward]
Net income	154.9				154.9
Stock-based compensation	15.4		6.1	$ 9.3
Shares issued under stock plans (shares)		100,000		(900,000)
Shares issued under stock plans	$ 33.7	$ 0.0	(32.8)	$ 66.5
Shares purchased under share repurchase program (shares)	800,000			800,000
Shares purchased under share repurchase program	$ (70.8)			$ (70.8)
Shares repurchased for employee tax withholdings (shares)		0
Shares repurchased for employee tax withholdings	(4.4)		0.2	(4.6)
Dividends declared	(31.8)				(31.8)
Other comprehensive income, net of tax	(36.5)					(36.5)
Balance at Sep. 30, 2018	1,351.8	$ 18.8	$ 282.8	$ (108.7)	1,312.7	$ (153.8)
Balance (in shares) at Sep. 30, 2018		75,300,000		1,200,000
Increase (Decrease) in Equity [Roll Forward]
Effect of modified retrospective application of a new accounting standard	$ 11.4				$ 11.4