Earnings Per Share Components of Basic and Diluted Shares Used In EPS Calculation (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Anti-dilutive shares	0.0	0.1
Weighted-average basic common shares outstanding	240.9	240.2
Potential number of shares issuable upon exercise of in-the-money stock options under the Long-Term Stock Incentive Plan	0.0	0.1
Average diluted common shares outstanding	240.9	240.3