PENSION BENEFITS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Change in benefit obligations:
Service cost	$ 2,213	$ 2,615
Interest cost	2,341	2,588
Recognized prior service cost	(179)	(179)
Components of net periodic benefit cost:
Service cost	2,213	2,615
Interest cost	2,341	2,588
Expected return on assets	(2,613)	(2,694)
Recognized prior service cost	(179)	(179)
Recognized net loss	1,690	1,976
Net periodic benefit cost	$ 3,452	$ 4,306