Income Taxes - Net Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Assets:
Deferred tax asset		$ (769)
Deferred charges and other	$ (5)	(17)
Liabilities
Other current liabilities		28
Deferred income taxes	1,072	9,499
Net deferred income tax liability	$ 1,067	$ 8,741