Fair Value (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Financial assets (liabilities)
Long-term debt, including current portion	$ (3,911)		$ (3,909)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets (liabilities)
Held-to-maturity marketable securities	10	[1]
Available-for-sale securities	123	[1]	134	[1]
Derivatives	0	[1]	0	[1]
Long-term debt, including current portion	0	[1]	0	[1]
Significant Other Observable Inputs (Level 2)
Financial assets (liabilities)
Held-to-maturity marketable securities	490	[1],[2]
Available-for-sale securities	65	[1],[2]	49	[1],[2]
Derivatives	(276)	[1],[2]	10	[1],[2]
Long-term debt, including current portion	(3,911)	[1],[2]	(3,758)	[1],[2]
Significant Unobservable Inputs (Level 3)
Financial assets (liabilities)
Investments, Fair Value Disclosure	0		0
Reported Value Measurement [Member]
Financial assets (liabilities)
Held-to-maturity marketable securities	500	[1]
Available-for-sale securities	188	[1]	183	[1]
Derivatives	(276)	[1]	10	[1]
Long-term debt, including current portion	(3,911)	[1]	(3,909)	[1]
Estimate of Fair Value Measurement [Member]
Financial assets (liabilities)
Held-to-maturity marketable securities	500	[1]
Available-for-sale securities	188	[1]	183	[1]
Derivatives	(276)	[1]	10	[1]
Long-term debt, including current portion	$ (3,911)	[1]	$ (3,758)	[1]

[1] We had no Level 3 financial instruments on December 31, 2014 or 2013.

[2] 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.