Fair Value Of Assets And Liabilities (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Marketable securities:
Long-term debt, including current portion	$ (3,909)		$ (3,930)
Sales of held-to-maturity securities	211		0		0
Sales of held-to maturity securities carrying value	210
Carrying Value
Marketable securities:
Available-for-sale	0	[1]	70	[1]
Held-to-maturity	0	[1],[2]	178	[1]
Other investments	150	[1]	145	[1]
Derivatives	22	[1]	34	[1]
Long-term debt, including current portion	(3,909)	[1]	(3,930)	[1]
Fair Value
Marketable securities:
Available-for-sale	0	[1]	70	[1]
Held-to-maturity	0	[1],[2]	175	[1]
Other investments	150	[1]	145	[1]
Derivatives	22	[1]	34	[1]
Long-term debt, including current portion	(3,966)	[1]	(4,199)	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1)
Marketable securities:
Available-for-sale	0	[1]	8	[1]
Held-to-maturity	0	[1],[2]	0	[1]
Other investments	96	[1]	89	[1]
Derivatives	0	[1]	0	[1]
Long-term debt, including current portion	0	[1]	0	[1]
Significant Other Observable Inputs (Level 2)
Marketable securities:
Available-for-sale	0	[1],[3]	62	[1],[3]
Held-to-maturity	0	[1],[2],[3]	175	[1],[3]
Other investments	54	[1],[3]	56	[1],[3]
Derivatives	22	[1],[3]	34	[1],[3]
Long-term debt, including current portion	$ (3,966)	[1],[3]	$ (4,199)	[1],[3]

[1] We had no Level 3 financial instruments on December 31, 2011 or 2012.

[2] We sold $211 of held-to-maturity securities in 2012. The net carrying amount of these securities on the date of sale was $210.

[3] Determined under a market approach using valuation models that incorporate observable inputs such as interest rates, bond yields and quoted prices for similar assets and liabilities.