COMMITMENTS AND CONTINGENCIES - Schedule of Outstanding Off-balance sheet Arrangements (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Other Commitments [Line Items]
Commitment amount	$ 64,192	$ 62,918
Undrawn commitments to extend credit
Other Commitments [Line Items]
Commitment amount	61,934	60,872
Financial standby letters of credit
Other Commitments [Line Items]
Commitment amount	2,080	1,892
Performance letters of credit
Other Commitments [Line Items]
Commitment amount	42	40
Commercial letters of credit
Other Commitments [Line Items]
Commitment amount	68	43
Marketing rights
Other Commitments [Line Items]
Commitment amount	41	44
Risk participation agreements
Other Commitments [Line Items]
Commitment amount	20	19
Residential mortgage loans sold with recourse
Other Commitments [Line Items]
Commitment amount	$ 7	$ 8