Fair Value of Financial Instruments - Carrying Values and Fair Values of Non-Current Financial Assets and Liabilities (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior, mezzanine, and other loans	$ 147	$ 142
Other noncurrent liabilities	(2,283)	(2,610)
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior, mezzanine, and other loans	147	142
Total noncurrent financial assets	147	142
Senior Notes	(4,487)	(5,087)
Commercial paper	(2,998)	(2,371)
Other long-term debt	(209)	(217)
Other noncurrent liabilities	(174)	(178)
Total noncurrent financial liabilities	(7,868)	(7,853)
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior, mezzanine, and other loans	133	130
Total noncurrent financial assets	133	130
Senior Notes	(4,404)	(5,126)
Commercial paper	(2,998)	(2,371)
Other long-term debt	(211)	(221)
Other noncurrent liabilities	(174)	(178)
Total noncurrent financial liabilities	$ (7,787)	$ (7,896)