LOANS AND LEASES - Reserve for Commercial TDRs Included in Allowance for Credit Losses (Detail) - USD ($)	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Modifications [Line Items]
Total allowance on acquired loans	$ 165,699,000	$ 160,782,000	$ 158,059,000	$ 154,369,000	$ 147,800,000	$ 142,012,000
Valuation for impairment of loans with pooled reserves	500,000		500,000
Total Commercial Loans and Leases [Member]
Financing Receivable, Modifications [Line Items]
Total allowance on acquired loans	105,188,000	$ 103,472,000	97,906,000	$ 98,950,000	$ 94,579,000	$ 85,305,000
Specific Reserves for Commercial TDRs [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Modifications [Line Items]
Total allowance on acquired loans	275,000		291,000
Pooled Reserves for Individual Commercial Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Modifications [Line Items]
Total allowance on acquired loans	$ 257,000		$ 276,000