Earnings Per Share (Antidilutive Securities Excluded From the Computation of Diluted Earnings Per Share) (Details) - $ / shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings, Shares	0.8	0.4	0.5	0.6
Antidilutive stock options based on application of the treasury stock method
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings, Shares	0.8	0.4	0.5	0.3
Antidilutive securities excluded from computation of earnings, Exercise Price Per Share	$ 108.61	$ 110.26	$ 108.35	$ 110.32
Antidilutive stock options due to net loss available to holders of Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings, Shares	0.0	0.0	0.0	0.0
Antidilutive shares based on application of the treasury stock method
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings, Shares	0.0	0.0	0.0	0.3
Antidilutive shares due to net loss available to holders of Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings, Shares	0.0	0.0	0.0	0.0