ACCUMULATED OTHER COMPREHENSIVE LOSS (AOCL) - RECLASSIFICATIONS OUT OF AOCL (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Operations										$ 148,672	$ 140,260	$ 120,205
Interest Charges										31,622	29,560	18,825
Other Income										(9,510)	(11,819)	(10,979)
Equity in Loss of Affiliated Companies										27,812	7,785	(1,585)
Income Taxes		$ (1,006)	$ (10,968)	$ (3,279)	$ 16,613	$ 10,415	$ (8,325)	$ (9,510)	$ 11,869	1,360	4,449	(19,014)
Income from Continuing Operations		$ (50,948)	$ 12,532	$ (13,341)	$ (53,853)	$ (43,992)	$ 4,276	$ (9,701)	$ (48,211)	$ (105,610)	$ (97,628)	$ (82,389)
Combined statutory tax rate										40.00%	40.00%	41.00%
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income from Continuing Operations										$ 4,408
Reclassification out of Accumulated Other Comprehensive Income [Member] | Actuarial Loss on Postretirement Benefits [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Operations										6,763
Income Taxes	[1]									(2,672)
Income from Continuing Operations										4,091
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gain on Derivatives-Other - interest rate contracts designated as cash flow hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest Charges										551
Income Taxes	[1]									(230)
Income from Continuing Operations										321
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Loss on Available-for-Sale Securities [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other Income										37
Income Taxes	[1]									(14)
Income from Continuing Operations										23
Reclassification out of Accumulated Other Comprehensive Income [Member] | Income of Affiliated Companies [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Equity in Loss of Affiliated Companies										(45)
Income Taxes	[1]									18
Income from Continuing Operations										$ (27)

[1] Determined using a combined average statutory tax rate of 40%.