REVENUE FROM CONTRACTS WITH CUSTOMERS - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Service charges on deposit accounts	$ 12,690	$ 10,535	$ 33,531	$ 31,714
Other service charges, commissions and fees	777	699	2,193	2,137
Service charges on deposit accounts
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	12,690	10,535	33,531	31,714
Debit card interchange fees
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	4,996	3,938	13,785	12,127
Overdraft fees
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	4,976	4,572	13,171	13,424
Other service charges on deposit accounts
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	2,718	2,025	6,575	6,163
Other service charges, commissions and fees
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	697	619	1,991	1,948
ATM fees
Disaggregation of Revenue [Line Items]
ASC 606 Revenue Items	697	619	1,991	1,948
Other
Disaggregation of Revenue [Line Items]
Other service charges, commissions and fees	$ 80	$ 80	$ 202	$ 189