EMPLOYEE BENEFITS (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Components of net periodic benefit cost (credit)
Service cost	$ 1,949	$ 2,178	$ 1,953
Interest cost	6,019	6,624	6,676
Expected return on plan assets	(8,508)	(9,025)	(9,555)
Amortization of prior service credit	(311)	(311)	(318)
Amortization of transition asset	0	(214)	(258)
Settlement loss	118	633	16
Special termination benefits	0	0	235
Amortization of loss (gain)	3,740	3,645	3,273
Net periodic cost (benefit)	3,007	3,530	2,022
Other Postretirement Benefits Plan [Member]
Components of net periodic benefit cost (credit)
Service cost	12	11	12
Interest cost	73	76	74
Expected return on plan assets	0	0	0
Amortization of prior service credit	0	0	0
Amortization of transition asset	0	0	0
Settlement loss	0	0	0
Special termination benefits	0	0	0
Amortization of loss (gain)	(43)	(58)	(51)
Net periodic cost (benefit)	$ 42	$ 29	$ 35