Share-based Compensation Plans (Narrative) (Details) shares in Millions	3 Months Ended
	Mar. 31, 2018 shares
SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	10.6
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	2.9
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0.4