Long-term Debt - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt, fair value	$ 16,900	$ 16,800
Short-term borrowings and current portion of long-term debt	2,224	3,153
Long-term debt, carrying amount	16,600	16,463
Commercial paper borrowings
Debt Instrument [Line Items]
Short-term borrowings and current portion of long-term debt	200	200
Long-term debt, carrying amount	2,833	2,421
Long-term debt	$ 3,000	$ 2,600