DEBT - Short-Term Borrowings (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Commercial paper	$ 10,088	$ 9,989
Other borrowings	16,039	20,712
Total short-term borrowings	26,127	30,701
Collateralized short-term advances from Federal Home Loan Bank	$ 6,300	$ 12,000