NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Allowance for loan and lease losses (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Financing Receivable Allowance For Credit Losses [Line Items]
Commercial And Construction Large Relationships Percent	80.00%
Boat Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable, Individually Evaluated for Impairment	$ 1
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable, Individually Evaluated for Impairment	1
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable, Individually Evaluated for Impairment	1
Construction Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable, Individually Evaluated for Impairment	$ 1