PENSION BENEFITS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Components of net periodic benefit cost [Abstract]
Service cost	$ 2,615	$ 2,234	$ 5,230	$ 4,468
Interest cost	2,588	2,339	5,176	4,678
Expected return on assets	(2,693)	(2,634)	(5,387)	(5,268)
Amortization of unrecognized transition amount		5		10
Recognized prior service cost	(180)	(192)	(359)	(384)
Recognized net loss	1,976	926	3,952	1,852
Net periodic benefit cost	$ 4,306	$ 2,678	$ 8,612	$ 5,356