Discontinued Operations - Operating Results for Cross-Border Energy Lease Investments (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Discontinued Operations And Disposal Groups [Abstract]
Income tax expense (benefit), income from operations of discontinued operations	$ 0	$ 5	$ 0	$ (43)
Income tax expense (benefit) from discontinued operations	$ 0	$ 5	$ 0	$ 5

Income tax expense or benefit attributable to Income or Loss from discontinued operations during the phase-out period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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