Employee Incentive, Retirement, Deferred Compensation, and Career Achievement Plans (Stock-Based Compensation Expense and Related Income Tax Benefit) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense		$ 153	$ 141	$ 135
Income tax benefit on share-based compensation expense		(57)	(53)	(51)
Income tax benefit	[1]	(1,296)	(1,104)	(832)
Accounting Standards Update 2016-09 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefit		87
Stock option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense		50	45	46
Restricted stock unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense		94	89	83
Employee stock purchase plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense		$ 9	$ 7	$ 6

[1] Includes the prospective adoption of ASU 2016-09 in 2017. See New Accounting Standards in Note 2 for additional information. Taxes on income were increased by approximately $46 million in December 2017 due to the enactment of the Tax Cuts and Jobs Act legislation resulting in the remeasurement of deferred tax assets and other tax adjustments.