Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Loss Contingencies [Line Items]
Rental expense under operating lease agreements	$ 411	$ 322
Capital Lease Obligations, Current	4,400		$ 4,000
Capital Lease Obligations, Noncurrent	5,800		5,100
Finance Lease Obligations, Current	159		144
Finance Lease Obligations, Noncurrent	2,500		2,400
Tax contingencies	1,800		1,700
Purchase Obligation of Business Acquisition	580
Pledged Assets	$ 971		$ 715