Shareholders' Equity (Shareholders' Equity, Accumulated Other Comprehensive Loss, Common Stock, and Preferred Stock) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Stock Repurchased During Period, Shares		0
Issued		1,069,000,000	1,070,000,000
In treasury		(196,000,000)	(204,000,000)
Total shares of common stock outstanding		873,000,000	866,000,000
Defined benefit and other postretirement liability adjustments	[1]	$ (334,000,000)	$ (313,000,000)
Cumulative translation adjustment		(80,000,000)	(80,000,000)
Other		(55,000,000)	(61,000,000)
Total accumulated other comprehensive loss		(469,000,000)	(454,000,000)
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Stock authorized to repurchase		$ 5,700,000,000
Number of shares of common stock repurchased from inception (in shares)		201,000,000
Approximate value of shares of common stock repurchased from inception		$ 8,400,000,000
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Number of shares of preferred stock that are authorized for issuance (in shares)		5,000,000
Number of shares preferred stock that are issued at period end (in shares)		0
Foreign Plan [Member]
Class of Stock [Line Items]
Net actuarial losses		$ 295,000,000	$ 290,000,000

[1] Included net actuarial losses for our international pension plans of $295 million at December 31, 2017 and $290 million at December 31, 2016.