Asset Impairments and Unusual Items - Components of (Income) Expense from Divestitures, Asset Impairments and Unusual Items (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Expense From Divestitures Asset Impairments And Unusual Items [Line Items]
(Income) expense from divestitures		$ 1	$ (1)
Asset impairments	83	9
Other			(77)
(Income) expense from divestitures, asset impairments and unusual items	$ 83	$ 10	$ (78)