LOANS AND LEASES - Additional Information (Detail) - USD ($)		6 Months Ended		12 Months Ended
	Dec. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	$ 14,896,943,000	$ 20,533,298,000		$ 14,896,943,000
Reclassification from non-accretable difference		$ 40,304,000	$ 14,508,000
Sustained period of delinquency for impairment evaluation		90 days	90 days
Minimum reserves for commercial loan		$ 500,000
Minimum amount to allocate specific valuation allowance		500,000
Interest income on impaired loans		2,600,000	$ 2,200,000
Restructured loans returned to performing status		3,500,000
Valuation for impairment of loans with pooled reserves	500,000	500,000		500,000
Pooled reserves for all other classes of loans		3,700,000		3,700,000
Loan Purchased not Subject to ASC 310-30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, Fair value		778,400,000
Loans acquired and accounted for under ASC 310-30, Unpaid principal balance		791,300,000
Loans acquired and accounted for under ASC 310-30, Contractual cash flows not expected to be collected		122,900,000
Purchased Credit-Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	$ 7,100,000	$ 20,800,000		7,100,000
Credit Concentration Risk [Member] | Acquired Loans Receivable [Member] | Purchased Credit-Impaired Loans [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of portfolio	1.00%	0.30%
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for default non-accrual status of trade accounts receivable		90 days
Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for default non-accrual status of trade accounts receivable		120 days
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for default non-accrual status of trade accounts receivable		180 days
Carrying value of OREO through foreclosure	$ 5,300,000	$ 4,900,000		5,300,000
Mortgage loans on real estate, foreclosure		$ 11,200,000		$ 12,000,000