Unaudited Condensed Consolidated Statement Of Shareholders' Equity - 3 months ended Mar. 31, 2016 - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
BALANCE, shares at Dec. 31, 2015		120,562,149
BALANCE at Dec. 31, 2015	$ 2,349.3	$ 1.2	$ 5.2	$ 2,702.8	$ (359.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	95.9			95.9
Repurchases of common stock	(371.1)				(371.1)
Stock-based compensation expense	15.3		15.3
Shares awarded under stock-based compensation plans, including income tax benefit of $0.6	1.2		(5.3)		6.5
BALANCE, shares at Mar. 31, 2016		120,562,149
BALANCE at Mar. 31, 2016	$ 2,090.6	$ 1.2	$ 15.2	$ 2,798.7	$ (724.5)