LOANS AND LEASES - Summary of Payment Status of TDRs (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	$ 54	$ 48
Originated Loans and Leases [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	51	44
Acquired Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	3	4
Performing [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	19	18
Performing [Member] | Originated Loans and Leases [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	19	18
Performing [Member] | Acquired Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	0	0
Non-Performing [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	19	21
Non-Performing [Member] | Originated Loans and Leases [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	16	17
Non-Performing [Member] | Acquired Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	3	4
Non-Accrual [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	16	9
Non-Accrual [Member] | Originated Loans and Leases [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	16	9
Non-Accrual [Member] | Acquired Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	$ 0	$ 0