PENSION AND POSTRETIREMENT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension Benefits
Components of net periodic benefit cost (credit)
Service cost	$ 493	$ 566	$ 1,467	$ 1,695
Interest cost	1,510	1,662	4,511	5,010
Expected return on plan assets	(2,143)	(2,305)	(6,379)	(6,942)
Amortization of prior service credit	(79)	(64)	(233)	(191)
Amortization of transition asset	0	(78)	0	(234)
Amortization of loss (gain)	943	951	2,810	2,850
Settlement loss (gain)	45	765	75	765
Net periodic cost	769	1,497	2,251	2,953
Postretirement Benefits
Components of net periodic benefit cost (credit)
Service cost	3	3	9	9
Interest cost	18	19	54	57
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)	(33)	(42)
Settlement loss (gain)	0	0	0	0
Net periodic cost	$ 10	$ 8	$ 30	$ 24