Receivables - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2012
Sold receivables that remain uncollected		$ 37
Sale of customer receivables	304
Cash received for receivables	50
Deferred purchase price receivable	254
Additional funding received		155
Purchase price receivable		18
Accounts receivables		3,339
Cash collections		3,116
Gross cash outflows from deferred purchased receivables		3,339
Gross cash inflows from deferred purchased receivables		3,321
Maximum [Member]
Funding of customer receivables sold	250
Minimum [Member]
Funding of customer receivables sold	$ 50