COMMITMENTS AND CONTINGENCIES - Schedule of Outstanding Off-balance sheet Arrangements (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Commitment amount	$ 71,739	$ 65,159
Undrawn commitments to extend credit
Other Commitments [Line Items]
Commitment amount	69,553	62,959
Letters of credit
Other Commitments [Line Items]
Commitment amount	2,125	2,136
Marketing rights
Other Commitments [Line Items]
Commitment amount	37	41
Risk participation agreements
Other Commitments [Line Items]
Commitment amount	19	16
Residential mortgage loans sold with recourse
Other Commitments [Line Items]
Commitment amount	$ 5	$ 7