Earnings Per Share (Reconciliation of Basic Shares Outstanding to Diluted Shares Outstanding) (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Basic shares outstanding	53.0	55.5	53.5	55.6
Dilutive effect of common stock equivalents	0.5	0.5	0.4	0.4
Diluted shares outstanding	53.5	56.0	53.9	56.0