DERIVATIVE INSTRUMENTS (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Fair value of the Company's derivative financial instruments as well as their classification on the consolidated statements of condition
Notional amount, asset derivatives	$ 126,000		$ 126,000
Net gains recognized on derivative instruments	396,000	$ 4,500,000	1,100,000	$ 5,700,000
Other assets
Fair value of the Company's derivative financial instruments as well as their classification on the consolidated statements of condition
Notional amount, asset derivatives	743,702,000		743,702,000		$ 566,147,000
Fair value of asset derivatives	7,487,000		7,487,000		6,378,000
Other liabilities.
Fair value of the Company's derivative financial instruments as well as their classification on the consolidated statements of condition
Notional amount, liability derivatives	126,000		126,000
Interest rate lock commitments | Other assets
Fair value of the Company's derivative financial instruments as well as their classification on the consolidated statements of condition
Notional amount, asset derivatives	361,105,000		361,105,000		264,359,000
Fair value of asset derivatives	7,396,000		7,396,000		6,253,000
Forward commitments to sell mortgage-backed securities | Other assets
Fair value of the Company's derivative financial instruments as well as their classification on the consolidated statements of condition
Notional amount, asset derivatives	382,597,000		382,597,000		301,788,000
Fair value of asset derivatives	91,000		91,000		$ 125,000
Interest rate swap contracts
Fair value of the Company's derivative financial instruments as well as their classification on the consolidated statements of condition
Notional amount of interest rate swaps	$ 10,300,000		$ 10,300,000