Income Taxes - Allocation of Total Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Tax Benefit/(Loss) Applicable To: [Abstract]
Income/(loss) from continuing operations, before income taxes	$ 4	$ 167	$ (188)	$ 309
Discontinued operations	$ 0	$ 2	$ 0	$ 13
Effective tax rate benefit	(8.70%)	30.10%	2.70%	31.00%

Tax effect allocated to a disposal group that is classified as a component of the entity reported as a separate component of income before extraordinary items. Includes the tax effects of the following: income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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