COMMITMENTS AND CONTINGENCIES - Schedule of Outstanding Off-balance sheet Arrangements (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Other Commitments [Line Items]
Commitment amount	$ 72,568	$ 71,739
Commitments to extend credit
Other Commitments [Line Items]
Commitment amount	70,217	69,553
Letters of credit
Other Commitments [Line Items]
Commitment amount	2,252	2,125
Marketing rights
Other Commitments [Line Items]
Commitment amount	35	37
Risk participation agreements
Other Commitments [Line Items]
Commitment amount	41	19
Loans sold with recourse
Other Commitments [Line Items]
Commitment amount	$ 23	$ 5