PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Net periodic benefit cost [Abstract]
Service Cost	$ 4,510	$ 5,421	$ 4,533
Interest Cost	10,735	9,439	9,622
Expected Return on Plan Assets	(13,491)	(11,914)	(10,341)
Amortizations:
Prior Service Cost (Credits)	175	251	251
Actuarial Loss	5,716	9,006	7,629
Net Periodic Benefit Cost	7,645	12,203	11,694
Capitalized Benefit Costs	(3,047)	(5,002)	(4,684)
Total Net Periodic Benefit Expense	4,598	7,201	7,010
Other Postretirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service Cost	891	1,139	1,037
Interest Cost	2,852	2,730	3,001
Expected Return on Plan Assets	(2,603)	(2,378)	(2,105)
Amortizations:
Prior Service Cost (Credits)	152	(283)	(283)
Actuarial Loss	974	1,738	1,725
Net Periodic Benefit Cost	2,266	2,946	3,375
Capitalized Benefit Costs	(722)	(1,172)	(1,340)
Total Net Periodic Benefit Expense	$ 1,544	$ 1,774	$ 2,035