Long Term Debt (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Other debt	$ 478	$ 419
Total long-term debt	7,200	6,966
Less: unamortized discounts	(892)	(506)
Total long-term debt, net of unamortized discounts	6,308	6,460
Less: current maturities of long-term debt	(150)
Total long-term debt, net	6,158	6,460
2.13% to 6.15%, due 2016 to 2042
Debt Instrument [Line Items]
Notes	5,642	5,308
7.00% To 7.75%, Due 2013 To 2036
Debt Instrument [Line Items]
Notes	$ 1,080	$ 1,239