INCOME TAXES (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax at Statutory Rate									$ 35,727,000	$ 22,181,000	$ 36,490,000
Increase (Decrease) Resulting from:
State Income Taxes									1,960,000	971,000	5,857,000
ESOP									(1,232,000)	(1,176,000)	(1,141,000)
Amortization of Investment Tax Credits - Utility									(211,000)	(258,000)	(287,000)
AFUDC									(1,481,000)	(916,000)	(1,048,000)
Investment and Other Tax Credits									(30,661,000)	(38,179,000)	(26,574,000)
Other - Net									347,000	(1,637,000)	(1,818,000)
Income Taxes: Continuing Operations	10,415,000	(8,325,000)	(9,510,000)	11,869,000	(9,621,000)	(5,533,000)	(11,632,000)	7,772,000	4,449,000	(19,014,000)	11,479,000
Income Taxes: Discontinued Operations									(312,000)	(426,000)	(629,000)
Net Income Taxes									4,137,000	(19,440,000)	10,850,000
Current:
Federal									(62,000)	(273,000)	(8,761,000)
State									3,052,000	3,066,000	221,000
Total Current									2,990,000	2,793,000	(8,540,000)
Deferred:
Federal									1,707,000	(19,978,000)	11,515,000
State									(37,000)	(1,571,000)	8,791,000
Total Deferred									1,670,000	(21,549,000)	20,306,000
Investment Tax Credits									(211,000)	(258,000)	(287,000)
Income Taxes: Continuing Operations	10,415,000	(8,325,000)	(9,510,000)	11,869,000	(9,621,000)	(5,533,000)	(11,632,000)	7,772,000	4,449,000	(19,014,000)	11,479,000
Income Taxes: Discontinued Operations									(312,000)	(426,000)	(629,000)
Annual amortization rate of investment tax credits									3.00%
Current:
Current Deferred Tax (Asset) Liability - Net	(57,748,000)				(30,609,000)				(57,748,000)	(30,609,000)
Noncurrent:
Noncurrent Deferred Tax Liability - Net	344,520,000				319,368,000				344,520,000	319,368,000
Accrued interest and penalties on unrecognized tax benefits	700,000				600,000				700,000	600,000	600,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1,				547,000				503,000	547,000	503,000	736,000
Increase as a result of tax positions taken in prior years									5,000	44,000	108,000
Decrease due to a lapse in the statute of limitations									0	0	(341,000)
Settlements									0	0	0
Balance at December 31,	552,000				547,000				552,000	547,000	503,000
Internal Revenue Service (IRS) [Member]
Noncurrent:
Operating loss carryforwards	427,452,000								427,452,000
Tax credit carryforwards	153,570,000								153,570,000
Alternative minimum tax credits	1,200,000								1,200,000
Internal Revenue Service (IRS) [Member] | 2030 [Member]
Noncurrent:
Tax credit carryforwards	11,628,000								11,628,000
Internal Revenue Service (IRS) [Member] | 2031 [Member]
Noncurrent:
Operating loss carryforwards	163,880,000								163,880,000
Tax credit carryforwards	26,613,000								26,613,000
Internal Revenue Service (IRS) [Member] | 2032 [Member]
Noncurrent:
Operating loss carryforwards	43,724,000								43,724,000
Tax credit carryforwards	32,071,000								32,071,000
Internal Revenue Service (IRS) [Member] | 2033 [Member]
Noncurrent:
Operating loss carryforwards	73,725,000								73,725,000
Tax credit carryforwards	46,179,000								46,179,000
Internal Revenue Service (IRS) [Member] | 2034 [Member]
Noncurrent:
Operating loss carryforwards	146,123,000								146,123,000
Tax credit carryforwards	37,079,000								37,079,000
State and Local Jurisdiction [Member]
Noncurrent:
Operating loss carryforwards	124,985,000								124,985,000
State and Local Jurisdiction [Member] | 2031 [Member]
Noncurrent:
Operating loss carryforwards	45,866,000								45,866,000
State and Local Jurisdiction [Member] | 2032 [Member]
Noncurrent:
Operating loss carryforwards	19,356,000								19,356,000
State and Local Jurisdiction [Member] | 2033 [Member]
Noncurrent:
Operating loss carryforwards	40,134,000								40,134,000
State and Local Jurisdiction [Member] | 2034 [Member]
Noncurrent:
Operating loss carryforwards	19,629,000								19,629,000
Classified as Current [Member]
Current:
Net Operating Loss Carryforward	(42,839,000)				(26,800,000)				(42,839,000)	(26,800,000)
Derivatives / Unrealized Gain	(7,965,000)				(8,608,000)				(7,965,000)	(8,608,000)
Conservation Incentive Program	(2,027,000)				4,631,000				(2,027,000)	4,631,000
Budget Billing - Customer Accounts	1,138,000				1,152,000				1,138,000	1,152,000
Provision for Uncollectibles	(6,296,000)				(1,994,000)				(6,296,000)	(1,994,000)
Other	241,000				1,010,000				241,000	1,010,000
Noncurrent:
Derivatives / Unrealized Gain	(7,965,000)				(8,608,000)				(7,965,000)	(8,608,000)
Net Operating Loss Carryforward	(42,839,000)				(26,800,000)				(42,839,000)	(26,800,000)
Classified as Noncurrent [Member]
Current:
Net Operating Loss Carryforward	(114,335,000)				(90,818,000)				(114,335,000)	(90,818,000)
Derivatives / Unrealized Gain	(4,589,000)				2,149,000				(4,589,000)	2,149,000
Noncurrent:
Book versus Tax Basis of Property	558,960,000				476,039,000				558,960,000	476,039,000
Deferred Gas Costs - Net	22,959,000				1,330,000				22,959,000	1,330,000
Environmental	12,147,000				13,017,000				12,147,000	13,017,000
Deferred Regulatory Costs	6,333,000				13,665,000				6,333,000	13,665,000
Deferred State Tax	(21,548,000)				(17,949,000)				(21,548,000)	(17,949,000)
Investment Tax Credit Basis Gross-Up	(77,000)				(185,000)				(77,000)	(185,000)
Deferred Pension & Other Post Retirement Benefits	39,891,000				24,218,000				39,891,000	24,218,000
Pension & Other Post Retirement Benefits	(34,892,000)				(17,777,000)				(34,892,000)	(17,777,000)
Deferred Revenues	(11,647,000)				(9,593,000)				(11,647,000)	(9,593,000)
Derivatives / Unrealized Gain	(4,589,000)				2,149,000				(4,589,000)	2,149,000
Net Operating Loss Carryforward	(114,335,000)				(90,818,000)				(114,335,000)	(90,818,000)
Investment and Other Tax Credits	(154,805,000)				(117,726,000)				(154,805,000)	(117,726,000)
Equity In Loss Of Affiliated Companies	39,230,000				37,764,000				39,230,000	37,764,000
Other	$ 6,893,000				$ 5,234,000				$ 6,893,000	$ 5,234,000