LOANS AND LEASES - Additional Allowance for Credit Losses Relating to Acquired Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	$ 179,247	$ 175,380	$ 160,782	$ 158,059
Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	6,837	6,698	$ 6,568	$ 7,268
Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	2,732	4,976
Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	1,785	(415)
Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	4,517	4,561
Acquired Loans [Member] | Direct Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	1,804	1,553
Acquired Loans [Member] | Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	518	484
Acquired Loans [Member] | Indirect Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	240	177
Acquired Loans [Member] | Consumer Lines of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	(242)	(77)
Acquired Loans [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	$ 2,320	$ 2,137