CONDENSED CONSOLIDATED STATEMENT OF EQUITY (UNAUDITED) - 3 months ended Mar. 31, 2017 - USD ($) shares in Millions, $ 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, 2016	$ 1,117.5	$ 18.4	$ 260.4	$ (46.1)	$ 1,071.6	$ (186.8)
Balance (in shares) at Dec. 31, 2016		73.7
Increase (Decrease) in Equity [Roll Forward]
Net income	60.9				60.9
Stock-based compensation	6.8		(0.7)	7.5
Shares issued under stock plans (shares)		0.7
Shares issued under stock plans	20.0	$ 0.2	16.7	3.1
Shares repurchased under share repurchase program	(26.9)			(26.9)
Shares repurchased for employee tax withholdings (shares)		0.0
Shares repurchased for employee tax withholdings	(3.8)		(0.4)	(3.4)
Dividends declared	(9.6)				(9.6)
Other comprehensive income, net of tax	7.8					7.8
Balance at Mar. 31, 2017	1,168.6	$ 18.6	$ 276.0	$ (65.8)	1,118.8	$ (179.0)
Balance (in shares) at Mar. 31, 2017		74.4
Increase (Decrease) in Equity [Roll Forward]
Effect of modified retrospective application of a new accounting standard	$ (4.1)				$ (4.1)