Earnings Per Share (Narrative) (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]
Weighted average shares excluded from denominator for diluted earnings per share because the stock options were anti-dilutive			0.4	0.5
Issuance of common stock under Equity Units stock purchase contracts			6.0
Restricted stock units issued under stock incentive plan	0.0	0.2	0.9	0.8
Restricted stock units excluded from the denominator for diluted earnings per share			0.3	0.4