Compensation Plans (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation cost		$ 119	$ 128	$ 136
Income tax benefits related to stock-based compensation arrangements		$ 39	$ 42	$ 45
Equity and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Number Of Shares Reserved For Grant Or Settlement Of Awards	110,000,000
Shares in excess must be counted against maximum number of shares granted	30,000,000
Number Of Shares Each Share Counts Against maximum Once Base Threshold Is Exceeded	4.5
Shares authorized for future grants		37,000,000