PENSION BENEFITS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Components of net periodic benefit cost [Abstract]
Service cost	$ 2,684	$ 2,592
Interest cost	2,053	2,072
Expected return on assets	(2,743)	(3,670)
Amortization of unrecognized transition amount	5	5
Recognized prior service cost	(192)	(192)
Recognized net loss	1,524	1,379
Net periodic benefit cost	$ 3,331	$ 2,186