Borrowings - Short-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Short-term debt disclosures
Long-term debt - current maturities	$ 7,834	$ 6,239
Total short-term debt	8,061	7,513
Commercial paper
Short-term debt disclosures
Short-term debt		$ 899
Weighted-average interest rates for short-term loans (as a percent)		0.70%
Short-term loans
Short-term debt disclosures
Short-term debt	$ 227	$ 375
Weighted-average interest rates for short-term loans (as a percent)	8.30%	9.50%