Earnings Per Share (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0.4		0.3
Weighted-average basic common shares outstanding (in shares)	176.7	180.1	176.4	179.9
Potential number of shares issuable upon excerise of in-the-money stock options under the Long-term Stock Incentive Plan	0.0	0.0	0.0	0.0
Average diluted common shares outstanding (in shares)	176.7	180.1	176.4	179.9