LOANS AND LEASES - Summary of Payment Status of TDRs (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Modifications [Line Items]
Document Period End Date	Mar. 31, 2019
Troubled debt restructurings ("TDRs")	$ 48	$ 48
Originated Loans and Leases [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	43	44
Acquired Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	5	4
Performing [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	18	18
Performing [Member] | Originated Loans and Leases [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	18	18
Performing [Member] | Acquired Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	0	0
Non-Performing [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	20	21
Non-Performing [Member] | Originated Loans and Leases [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	16	17
Non-Performing [Member] | Acquired Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	4	4
Non-Accrual [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	10	9
Non-Accrual [Member] | Originated Loans and Leases [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	9	9
Non-Accrual [Member] | Acquired Loans [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings ("TDRs")	$ 1	$ 0