COMMITMENTS AND CONTINGENCIES - Schedule of Outstanding Off-balance sheet Arrangements (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Commitment amount	$ 65,290	$ 65,159
Undrawn commitments to extend credit
Other Commitments [Line Items]
Commitment amount	63,107	62,959
Financial standby letters of credit
Other Commitments [Line Items]
Commitment amount	1,966	2,036
Performance letters of credit
Other Commitments [Line Items]
Commitment amount	109	47
Commercial letters of credit
Other Commitments [Line Items]
Commitment amount	43	53
Marketing rights
Other Commitments [Line Items]
Commitment amount	41	41
Risk participation agreements
Other Commitments [Line Items]
Commitment amount	18	16
Residential mortgage loans sold with recourse
Other Commitments [Line Items]
Commitment amount	$ 6	$ 7