Earnings Per Share (Reconciliation of Basic Shares Outstanding to Diluted Shares Outstanding) (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Basic shares outstanding	53.3	55.6	53.7	55.6
Dilutive effect of common stock equivalents	0.4	0.4	0.4	0.3
Diluted shares outstanding	53.7	56.0	54.1	55.9