DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Narrative (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2010
Derivative [Line Items]
Interest rate cash flow hedge liability at fair value	$ 381,000				$ 978,000					$ 381,000	$ 978,000
Interest expense	10,041,000	$ 9,467,000	$ 8,254,000	$ 6,460,000	5,677,000	$ 5,143,000	$ 4,751,000	$ 4,123,000		34,222,000	19,694,000	$ 14,856,000
Mortgages
Derivative [Line Items]
Derivative asset	2,900,000				4,300,000					2,900,000	4,300,000
Derivative liability	67,000				0					67,000	0
Interest rate lock commitments | Mortgages
Derivative [Line Items]
Derivative asset, notional amount	$ 86,100,000				91,400,000					$ 86,100,000	91,400,000
Interest Rate Swap
Derivative [Line Items]
Derivative liability, notional amount													$ 37,100,000
Derivative, fixed interest rate	4.11%									4.11%
Interest expense										$ 484,000	678,000	$ 822,000
Forward contracts related to mortgage loans held for sale | Mortgages
Derivative [Line Items]
Derivative, notional amount	$ 158,300,000				$ 150,000,000					$ 158,300,000	$ 150,000,000
London Interbank Offered Rate (LIBOR) | Interest Rate Swap
Derivative [Line Items]
Derivative, basis spread on variable rate	1.63%									1.63%
Scenario, Forecast | Interest Rate Swap
Derivative [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net									$ 235,000