PENSION AND POSTRETIREMENT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Benefits
Components of net periodic benefit cost (credit)
Service cost	$ 487	$ 569	$ 974	$ 1,128
Interest cost	1,504	1,676	3,002	3,348
Expected return on plan assets	(2,126)	(2,328)	(4,236)	(4,637)
Amortization of prior service credit	(78)	(64)	(154)	(127)
Amortization of transition asset	0	(79)	0	(156)
Amortization of loss (gain)	935	957	1,867	1,900
Settlement loss (gain)	30	0	30	0
Net periodic cost	752	731	1,483	1,456
Postretirement Benefits
Components of net periodic benefit cost (credit)
Service cost	3	3	6	6
Interest cost	18	19	36	38
Expected return on plan assets	0	0	0	0
Amortization of prior service credit	0	0	0	0
Amortization of transition asset	0	0	0	0
Amortization of loss (gain)	(11)	(14)	(22)	(28)
Settlement loss (gain)	0	0	0	0
Net periodic cost	$ 10	$ 8	$ 20	$ 16