Asset Impairments and Unusual Items - Components of (Income) Expense from Divestitures, Asset Impairments (Other Than Goodwill) and Unusual Items (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Extraordinary and Unusual Items [Abstract]
(Income) expense from divestitures	$ (515)	$ (8)
Asset impairments (other than goodwill)	345	472	79
(Income) expense from divestitures, asset impairments (other than goodwill) and unusual items	$ (170)	$ 464	$ 79