Fair Value of Financial Instruments - Carrying Values and Fair Values of Non-Current Financial Assets and Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior, mezzanine, and other loans	$ 228	$ 245
Other noncurrent liabilities	(2,094)	(1,744)
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior, mezzanine, and other loans	228	245
Total noncurrent financial assets	228	245
Senior Notes	(5,088)	(5,438)
Commercial paper	(2,791)	(2,311)
Other long-term debt	(226)	(280)
Other noncurrent liabilities	(186)	(59)
Total noncurrent financial liabilities	(8,291)	(8,088)
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior, mezzanine, and other loans	216	231
Total noncurrent financial assets	216	231
Senior Notes	(5,161)	(5,394)
Commercial paper	(2,791)	(2,311)
Other long-term debt	(230)	(284)
Other noncurrent liabilities	(186)	(59)
Total noncurrent financial liabilities	$ (8,368)	$ (8,048)