CONDENSED CONSOLIDATED STATEMENT OF EQUITY (UNAUDITED) - 6 months ended Jun. 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	99.7				99.7
Stock-based compensation	11.5		2.2	$ 9.3
Shares issued under stock plans (shares)		100,000		(300,000)
Shares issued under stock plans	$ 12.3	$ 0.0	(7.0)	$ 19.3
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	(31.3)				(31.3)
Other comprehensive income, net of tax	(26.4)					(26.4)
Balance at Jun. 30, 2018	1,281.9	$ 18.8	$ 304.7	$ (155.9)	1,258.0	$ (143.7)
Balance (in shares) at Jun. 30, 2018		75,300,000		1,800,000
Increase (Decrease) in Equity [Roll Forward]
Effect of modified retrospective application of a new accounting standard	$ 11.4				$ 11.4