COMMITMENTS AND CONTINGENCIES - Schedule of Outstanding Off-balance sheet Arrangements (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Other Commitments [Line Items]
Commitment amount	$ 73,085	$ 71,739
Commitments to extend credit
Other Commitments [Line Items]
Commitment amount	70,825	69,553
Letters of credit
Other Commitments [Line Items]
Commitment amount	2,148	2,125
Marketing rights
Other Commitments [Line Items]
Commitment amount	33	37
Risk participation agreements
Other Commitments [Line Items]
Commitment amount	47	19
Loans sold with recourse
Other Commitments [Line Items]
Commitment amount	$ 32	$ 5