Consolidated Statements 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, Amount at Dec. 31, 2011	$ 1,894.6us-gaap_StockholdersEquity	$ 1.6	$ 19.6	$ 2,646.6	$ (773.2)
BALANCE, Shares at Dec. 31, 2011		163,562,149
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	316.4us-gaap_NetIncomeLoss			316.4
Repurchases of common stock	(582.3)				(582.3)
Stock-based compensation expense	18.6		18.6
Shares awarded under stock-based compensation plans, including excess income tax benefit of $18.0 in 2014, $10.0 in 2013, and $10.6 in 2012	41.2		(11.6)		52.8
BALANCE, Amount at Dec. 31, 2012	1,688.5us-gaap_StockholdersEquity	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	374.9us-gaap_NetIncomeLoss			374.9
Repurchases of common stock	(55.7)				(55.7)
Stock-based compensation expense	21.3		21.3
Shares awarded under stock-based compensation plans, including excess income tax benefit of $18.0 in 2014, $10.0 in 2013, and $10.6 in 2012	32.7		(5.1)		37.8
BALANCE, Amount at Dec. 31, 2013	2,061.7us-gaap_StockholdersEquity	1.6	42.8	3,337.9	(1,320.6)
BALANCE, Shares at Dec. 31, 2013		163,562,149
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	418.7us-gaap_NetIncomeLoss			418.7
Repurchases of common stock	(487.7)				(487.7)
Stock-based compensation expense	26.3		26.3
Shares awarded under stock-based compensation plans, including excess income tax benefit of $18.0 in 2014, $10.0 in 2013, and $10.6 in 2012	53.1		(7.3)		60.4
BALANCE, Amount at Dec. 31, 2014	$ 2,072.1us-gaap_StockholdersEquity	$ 1.6	$ 61.8	$ 3,756.6	$ (1,747.9)
BALANCE, Shares at Dec. 31, 2014		163,562,149

This element represents the amount of recognized equity-based compensation during the period, that is, the amount recognized as expense in the income statement (or as asset if compensation is capitalized). Alternate captions include the words "stock-based compensation".

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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- Definition

Value of stock (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of stock value of such awards forfeited. Stock issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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