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Supplemental Balance Sheet Information (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Changes in the liability for asset retirement obligations
Balance as of January 1	$ 114	$ 103
Accretion expense	2	2
Liabilities incurred/adjusted	(1)
Liabilities settled
Balance as of March 31	115	105
Supplemental Balance Sheet Information (Textual) [Abstract]
Net property, plant and equipment included in other current assets classified as assets held for sale	$ 0		$ 6

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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- Definition

Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

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