Debt (Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Total long-term debt	$ 5,826	$ 6,045
Less current portion	756	619
Long-term portion	5,070	5,426
Notes and Debentures [Member]
Weighted-average interest rate	5.53%
Total long-term debt	4,857	4,984
Dealer Remarketable Securities [Member]
Weighted-average interest rate	4.22%
Total long-term debt	200	200
Industrial Development Revenue Bonds [Member]
Weighted-average interest rate	0.24%
Total long-term debt	261	280
Bank Loans And Other Financings In Various Currencies [Member]
Weighted-average interest rate	2.57%
Total long-term debt	$ 508	$ 581