Discontinued Operations - (Loss) Income Recognized from Cross-Border Energy Lease Investments (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Schedule of Discontinued Operations [Line Items]
(Loss) income from discontinued operations, net of income taxes		$ (319)
Cross-Border Energy Lease Investments [Member]
Schedule of Discontinued Operations [Line Items]
Operating revenue from PHI's cross-border energy lease investments		5
Non-cash charge to reduce carrying value of PHI's cross-border energy lease investments		(373)
Total operating revenue		(368)
(Loss) income from operations of discontinued operations, net of income taxes		5
Net (losses) gains associated with the early termination of the cross-border energy lease investments, net of income taxes		(325)
(Loss) income from discontinued operations, net of income taxes		$ (320)