Income Taxes - Components of Total Deferred Taxes Table (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred Tax Assets (Liabilities), Net [Line Items]
Total deferred taxes	$ (8,527)	$ (8,885)
Federal [Member]
Deferred Tax Assets (Liabilities), Net [Line Items]
Total deferred taxes	(7,649)	(8,246)
State, net of federal [Member]
Deferred Tax Assets (Liabilities), Net [Line Items]
Total deferred taxes	(341)	(332)
Foreign [Member]
Deferred Tax Assets (Liabilities), Net [Line Items]
Total deferred taxes	$ (537)	$ (307)