PENSION AND OTHER POST-EMPLOYMENT BENEFITS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Benefits
PENSIONS AND OTHER POSTRETIREMENT BENEFITS
Service cost	$ 175	$ 468	$ 350	$ 936
Interest cost	2,390	2,416	4,780	4,832
Expected return on plan assets	(4,615)	(3,612)	(9,230)	(7,224)
Amortization of prior service credit	0	0	0	0
Recognized actuarial loss (gain)	154	123	308	246
Net periodic benefit (income) cost	(1,896)	(605)	(3,792)	(1,210)
Other Benefits
PENSIONS AND OTHER POSTRETIREMENT BENEFITS
Service cost	0	0	0	0
Interest cost	43	49	86	98
Expected return on plan assets	0	0	0	0
Amortization of prior service credit	(371)	(280)	(742)	(560)
Recognized actuarial loss (gain)	1	(62)	2	(124)
Net periodic benefit (income) cost	$ (327)	$ (293)	$ (654)	$ (586)