SECURITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available for sale:
Amortized Cost	$ 750,630	$ 775,903
Gross Unrealized Gains	58	306
Gross Unrealized Losses	(24,632)	(16,293)
Estimated Fair Value	726,056	759,916
Held to maturity:
Amortized Cost	176,089	180,866
Gross Unrealized Gains	723	1,293
Gross Unrealized Losses	(3,935)	(2,274)
Estimated Fair Value	172,877	179,885
Total securities
Amortized Cost	926,719	956,769
Gross Unrealized Gains	781	1,599
Gross Unrealized Losses	(28,567)	(18,567)
Total securities	898,933	939,801
U.S. GSE securities
Available for sale:
Amortized Cost	57,995	57,994
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,957)	(1,180)
Estimated Fair Value	56,038	56,814
State and municipal obligations
Available for sale:
Amortized Cost	86,127	87,582
Gross Unrealized Gains	54	259
Gross Unrealized Losses	(1,335)	(819)
Estimated Fair Value	84,846	87,022
Held to maturity:
Amortized Cost	58,511	60,762
Gross Unrealized Gains	586	972
Gross Unrealized Losses	(260)	(64)
Estimated Fair Value	58,837	61,670
U.S. GSE residential mortgage-backed securities
Available for sale:
Amortized Cost	181,005	189,705
Gross Unrealized Gains	4	29
Gross Unrealized Losses	(5,442)	(2,833)
Estimated Fair Value	175,567	186,901
Held to maturity:
Amortized Cost	10,988	11,424
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(433)	(261)
Estimated Fair Value	10,555	11,163
U.S. GSE residential collateralized mortgage obligations
Available for sale:
Amortized Cost	300,907	314,390
Gross Unrealized Gains	0	16
Gross Unrealized Losses	(10,233)	(7,016)
Estimated Fair Value	290,674	307,390
Held to maturity:
Amortized Cost	52,603	54,250
Gross Unrealized Gains	137	244
Gross Unrealized Losses	(1,153)	(666)
Estimated Fair Value	51,587	53,828
U.S. GSE commercial mortgage-backed securities
Available for sale:
Amortized Cost	5,976	6,017
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(120)	(40)
Estimated Fair Value	5,856	5,979
Held to maturity:
Amortized Cost	22,751	22,953
Gross Unrealized Gains	0	77
Gross Unrealized Losses	(719)	(438)
Estimated Fair Value	22,032	22,592
U.S. GSE commercial collateralized mortgage obligations
Available for sale:
Amortized Cost	48,370	49,965
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,878)	(1,249)
Estimated Fair Value	46,492	48,716
Held to maturity:
Amortized Cost	31,236	31,477
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,370)	(845)
Estimated Fair Value	29,866	30,632
Other asset backed securities
Available for sale:
Amortized Cost	24,250	24,250
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(849)	(849)
Estimated Fair Value	23,401	23,401
Corporate bonds
Available for sale:
Amortized Cost	46,000	46,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,818)	(2,307)
Estimated Fair Value	$ 43,182	$ 43,693