PENSION BENEFITS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Components of net periodic benefit cost [Abstract]
Service cost	$ 2,684	$ 2,592	$ 5,368	$ 5,184
Interest cost	2,053	2,072	4,106	4,144
Expected return on assets	(2,743)	(2,012)	(5,486)	(5,682)
Amortization of unrecognized transition amount	5	5	10	10
Recognized prior service cost	(192)	(192)	(384)	(384)
Recognized net loss	1,524	1,379	3,048	2,758
Net periodic benefit cost	$ 3,331	$ 3,844	$ 6,662	$ 6,030