Operating Results of Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues		$ 46
Operating expenses, including net gain on disposal of assets held for sale in 2011	(1)	99	[1]
(Loss) income before income tax benefit (expense) and equity in net income from unconsolidated investments	(1)	146
Equity in net income from unconsolidated investments	1	6
Income from discontinued operations, net of income tax expense of $0 and $2, respectively		$ 149

[1] During the first quarter of 2011, we recorded a net after-tax gain on disposal of assets held for sale of $136 million.