COMMITMENTS AND CONTINGENCIES - Schedule of Outstanding Off-balance sheet Arrangements (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Commitment amount	$ 67,598	$ 65,159
Undrawn commitments to extend credit
Other Commitments [Line Items]
Commitment amount	65,389	62,959
Financial standby letters of credit
Other Commitments [Line Items]
Commitment amount	1,974	2,036
Performance letters of credit
Other Commitments [Line Items]
Commitment amount	120	47
Commercial letters of credit
Other Commitments [Line Items]
Commitment amount	56	53
Marketing rights
Other Commitments [Line Items]
Commitment amount	39	41
Risk participation agreements
Other Commitments [Line Items]
Commitment amount	14	16
Residential mortgage loans sold with recourse
Other Commitments [Line Items]
Commitment amount	$ 6	$ 7