Income Taxes - Net Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets:
Deferred charges and other	$ 5	$ 5
Liabilities:
Deferred income taxes	1,710	2,529	[1]
Net deferred income tax liability	$ 1,705	$ 2,524

[1] Financial information for 2015 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.