CONDENSED CONSOLIDATED STATEMENT OF EQUITY (UNAUDITED) - 3 months ended Mar. 31, 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	43.6				43.6
Stock-based compensation	4.4		(4.8)	$ 9.2
Shares issued under stock plans (shares)		100,000		(100,000)
Shares issued under stock plans	$ 6.5	$ 0.0	3.8	$ 2.7
Shares purchased under share repurchase program (shares)	540,000			500,000
Shares purchased under share repurchase program	$ (47.9)			$ (47.9)
Shares repurchased for employee tax withholdings (shares)		0
Shares repurchased for employee tax withholdings	(3.7)		0.2	(3.9)
Dividends declared	(10.4)				(10.4)
Other comprehensive income, net of tax	21.5					21.5
Balance at Mar. 31, 2018	1,305.3	$ 18.8	$ 308.5	$ (149.0)	1,222.8	$ (95.8)
Balance (in shares) at Mar. 31, 2018		75,300,000		1,700,000
Increase (Decrease) in Equity [Roll Forward]
Effect of modified retrospective application of a new accounting standard	$ 11.4				$ 11.4