REVENUE FROM CONTRACTS WITH CUSTOMERS - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Service charges on deposit accounts	$ 10,613	$ 10,616	$ 20,841	$ 21,179
Other service charges, commissions and fees	697	729	1,416	1,438
Service charges on deposit accounts
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	10,613	10,616	20,841	21,179
Debit card interchange fees
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	4,580	4,143	8,789	8,189
Overdraft fees
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	4,087	4,408	8,195	8,852
Other service charges on deposit accounts
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	1,946	2,065	3,857	4,138
Other service charges, commissions and fees
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	632	656	1,294	1,329
ATM fees
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	632	656	1,294	1,329
Other
Disaggregation of Revenue [Line Items]
Other service charges, commissions and fees	$ 65	$ 73	$ 122	$ 109