Receivables (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Schedule Of Accounts Receivables [Line Items]
Sold receivables that remain uncollected	$ 219
Sale of customer receivables	304
Cash received for receivables	50
Deferred purchase price receivable	254
Maximum [Member]
Schedule Of Accounts Receivables [Line Items]
Funding of customer receivables sold	250
Minimum [Member]
Schedule Of Accounts Receivables [Line Items]
Funding of customer receivables sold	$ 50