Carrying Values and Estimated Fair Values of Our Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets
Notes and other	$ 552	[1]	$ 594	[1]
Liabilities
Debt, excluding capital lease obligations	(2,532)		(3,357)
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Notes and other	610		639
Liabilities
Debt, excluding capital lease obligations	$ (2,708)		$ (3,497)

[1] At September 30, 2012 and December 31, 2011, net of allowance for losses of $24 and $27.