Short-Term Borrowings - Unsecured Short-Term Borrowings (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Current portion of unsecured long-term borrowings	$ 26,288	$ 25,373
Hybrid financial instruments	12,737	12,956
Commercial paper		208
Other short-term borrowings	3,800	4,250
Total unsecured short-term borrowings	$ 42,825	$ 42,787
Unsecured short-term debt, weighted average interest rate, after giving effect to hedging activities	1.83%	1.52%