Earnings Per Share (Schedule of Weighted Average Shares Outstanding) (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Basic shares outstanding (in shares)	103.4	102.3	103.2	102.1
Effect of potential common stock:
Common stock awards (in shares)	1.2	1.4	1.2	1.3
Diluted shares outstanding (in shares)	104.6	103.7	104.4	103.4