Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Loss Contingencies [Line Items]
Rental expense under operating lease agreements	$ 267	$ 229	$ 533	$ 448
Tax contingencies	854		854		$ 710
Pledged Assets	$ 311		$ 311		$ 602