Unaudited Condensed Consolidated Statement Of Shareholders' Equity (USD $) In Millions, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
BALANCE at Dec. 31, 2012	$ 1,688.5	$ 1.6	$ 26.6	$ 2,963.0	$ (1,302.7)
BALANCE, shares at Dec. 31, 2012		163,562,149
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	172.9			172.9
Repurchases of common stock	(6.7)				(6.7)
Stock-based compensation expense	12.8		12.8
Shares awarded under stock-based compensation plans, including income tax benefit of $4.4	15.0		(4.5)		19.5
BALANCE at Jun. 30, 2013	$ 1,882.5	$ 1.6	$ 34.9	$ 3,135.9	$ (1,289.9)
BALANCE, shares at Jun. 30, 2013		163,562,149