Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Valuation and qualifying accounts:
Beginning balance			$ 244
Charged to cost and expenses			101
Write-offs			(53)
Other changes			5
Ending balance			297
Reserve for doubtful accounts receivable [Member]
Valuation and qualifying accounts:
Beginning balance	162	157	74
Charged to cost and expenses	84	39	94
Write-offs	(18)	(24)	(12)
Other changes	1	(10)	1
Ending balance	229	162	157
Reserve for inventories [Member]
Valuation and qualifying accounts:
Beginning balance	322	297
Charged to cost and expenses	16	33
Write-offs	(36)	(32)
Other changes	2	24
Ending balance	$ 304	$ 322