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Asset Retirement Obligations - Schedule of Changes in Carrying Value of Recorded AROs (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Asset Retirement Obligations [Line Items]
Balance at beginning of year	$ 579	$ 534
Accretion expense	25	22
Payments	(81)	(86)
Liabilities incurred	80	115
Foreign currency translation and other	7	(6)
Balance at end of year	$ 610	$ 579

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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