Shareholders' Equity (Shareholders' Equity, Accumulated Other Comprehensive Loss, Common Stock, and Preferred Stock) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Issued		1,066,000,000	1,068,000,000
In treasury		(181,000,000)	(190,000,000)
Total shares of common stock outstanding		885,000,000	878,000,000
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Defined benefit and other postretirement liability adjustments	[1]	$ (226,000,000)	$ (214,000,000)
Cumulative translation adjustment		(83,000,000)	(82,000,000)
Other		(53,000,000)	(66,000,000)
Total accumulated other comprehensive loss		$ (362,000,000)	$ (362,000,000)
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Stock Repurchased During Period, Shares		7,400,000	4,500,000
Treasury Stock, Value, Acquired, Cost Method		$ 100,000,000
Stock authorized to repurchase		$ 5,100,000,000
Number of shares of common stock repurchased from inception (in shares)		224,000,000
Approximate value of shares of common stock repurchased from inception		$ 9,000,000,000.0
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]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net actuarial losses		$ 212,000,000	$ 189,000,000

[1] Included net actuarial losses for our international pension plans of $212 million at December 31, 2020 and $189 million at December 31, 2019.