Earnings Per Share Components of Basic and Diluted Shares Used In EPS Calculation (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares	0.0	0.0	0.0	0.0
Weighted-average basic common shares outstanding	236.9	240.7	238.3	240.5
Potential number of shares issuable upon exercise of in-the-money stock options under the Long-Term Stock Incentive Plan	0.1	0.0	0.0	0.0
Average diluted common shares outstanding	237.0	240.7	238.3	240.5