Summary of Significant Accounting Policies (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction in other current assets	$ (318)	$ (573)
Reduction in short-term debt	(32)	(32)
Reduction in other assets	(2,239)	(2,268)
Reduction in long-term debt	$ (15,641)	(15,636)
Accounting Standards Update 2015-03 [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction in other current assets		1
Reduction in short-term debt		1
Reduction in other assets		82
Reduction in long-term debt		$ 82