SUPPLEMENTAL INFORMATION - Schedule of Fair Value of Derivatives, Assets (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Assets	$ 4,077,000,000	$ 5,467,000,000
Gross accrued interest	470,000,000	768,000,000
Gross derivatives recognized in statement of financial position	4,547,000,000	6,234,000,000
Amounts offset in statement of financial position
Netting adjustments	(1,606,000,000)	(3,097,000,000)
Cash collateral	(2,059,000,000)	(2,025,000,000)
Amounts offset in statement of financial position	(3,665,000,000)	(5,121,000,000)
Net derivatives	882,000,000	1,113,000,000
Securities held as collateral	(432,000,000)	(442,000,000)
Net amount	450,000,000	671,000,000
Cumulative adjustment for non-performance risk	(1,000,000)	(3,000,000)
Excluded excess cash collateral received	284,000,000	6,000,000
Excluded excess cash collateral posted	142,000,000	177,000,000
Excluded excess securities collateral received	68,000,000	0
Derivatives accounted for as hedges
Offsetting Assets [Line Items]
Assets	2,790,000,000	3,508,000,000
Derivatives accounted for as hedges | Interest rate contracts
Offsetting Assets [Line Items]
Assets	2,728,000,000	3,106,000,000
Derivatives accounted for as hedges | Currency exchange contracts
Offsetting Assets [Line Items]
Assets	62,000,000	402,000,000
Derivatives accounted for as hedges | Other contracts
Offsetting Assets [Line Items]
Assets	0	0
Derivatives not accounted for as hedges
Offsetting Assets [Line Items]
Assets	1,287,000,000	1,958,000,000
Derivatives not accounted for as hedges | Interest rate contracts
Offsetting Assets [Line Items]
Assets	58,000,000	62,000,000
Derivatives not accounted for as hedges | Currency exchange contracts
Offsetting Assets [Line Items]
Assets	1,132,000,000	1,778,000,000
Derivatives not accounted for as hedges | Other contracts
Offsetting Assets [Line Items]
Assets	$ 97,000,000	$ 119,000,000