PENSION AND OTHER POSTRETIREMENT BENEFITS 2 (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits [Member]
Regulatory Assets
Beginning Balance	$ 42,632	$ 68,713
Amounts Arising during the Period: Net Actuarial Loss (Gain)	31,075	(20,554)
Amounts Arising during the Period: Prior Service Cost	486
Amounts Amortized to Net Periodic Costs: Net Actuarial Loss	(2,841)	(5,319)
Amounts Amortized to Net Periodic Costs: Prior Service (Cost) Credit	(175)	(208)
Ending Balance	71,177	42,632
Accumulated Other Comprehensive Loss (pre-tax)
Beginning Balance	27,574	35,431
Amounts Arising during the Period: Net Actuarial Loss (Gain)	14,698	(4,173)
Amounts Arising during the Period: Prior Service Cost	14
Amounts Amortized to Net Periodic Costs: Net Actuarial Loss	(2,819)	(3,642)
Amounts Amortized to Net Periodic Costs: Prior Service (Cost) Credit	1	(42)
Ending Balance	39,468	27,574
Other Postretirement Benefits [Member]
Regulatory Assets
Beginning Balance	16,652	27,184
Amounts Arising during the Period: Net Actuarial Loss (Gain)	7,826	(9,171)
Amounts Arising during the Period: Prior Service Cost	4,146
Amounts Amortized to Net Periodic Costs: Net Actuarial Loss	(628)	(1,555)
Amounts Amortized to Net Periodic Costs: Prior Service (Cost) Credit	(133)	194
Ending Balance	27,863	16,652
Accumulated Other Comprehensive Loss (pre-tax)
Beginning Balance	3,710	4,195
Amounts Arising during the Period: Net Actuarial Loss (Gain)	2,269	(390)
Amounts Arising during the Period: Prior Service Cost	981
Amounts Amortized to Net Periodic Costs: Net Actuarial Loss	(187)	(177)
Amounts Amortized to Net Periodic Costs: Prior Service (Cost) Credit	(18)	82
Ending Balance	$ 6,755	$ 3,710