Income Taxes - Components of Total Deferred Taxes Table (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets (Liabilities), Net [Line Items]
Total deferred taxes	$ (5,400)	$ (8,527)
Federal [Member]
Deferred Tax Assets (Liabilities), Net [Line Items]
Total deferred taxes	(4,721)	(7,649)
State, net of federal [Member]
Deferred Tax Assets (Liabilities), Net [Line Items]
Total deferred taxes	(248)	(341)
Foreign [Member]
Deferred Tax Assets (Liabilities), Net [Line Items]
Total deferred taxes	$ (431)	$ (537)