INCOME TAXES (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at Statutory Rate									$ 36,490,000	$ 39,326,000	$ 33,634,000
Increase (Decrease) Resulting from:
State Income Taxes									5,857,000	6,763,000	5,669,000
ESOP									(1,141,000)	(1,063,000)	(971,000)
Amortization of Investment Tax Credits									(287,000)	(302,000)	(310,000)
Amortization of Flowthrough Depreciation									0	526,000	664,000
AFUDC									(1,048,000)	(729,000)	0
Investment and Other Tax Credits									(26,574,000)	(21,927,000)	(10,107,000)
Other - Net									(1,818,000)	(92,000)	232,000
Income Taxes: Continuing Operations									11,479,000	22,502,000	28,811,000
Income Taxes: Discontinued Operations									(629,000)	(302,000)	(337,000)
Net Income Taxes	(757,000)	(2,576,000)	(1,072,000)	15,884,000	3,022,000	(6,034,000)	3,004,000	22,510,000	10,850,000	22,200,000	28,474,000
Current:
Federal									(8,761,000)	(844,000)	(7,527,000)
State									221,000	345,000	7,753,000
Total Current									(8,540,000)	(499,000)	226,000
Deferred:
Federal									11,515,000	13,244,000	27,927,000
State									8,791,000	10,059,000	968,000
Total Deferred									20,306,000	23,303,000	28,895,000
Investment Tax Credits									(287,000)	(302,000)	(310,000)
Income Taxes: Continuing Operations									11,479,000	22,502,000	28,811,000
Income Taxes: Discontinued Operations									(629,000)	(302,000)	(337,000)
Net Income Taxes	(757,000)	(2,576,000)	(1,072,000)	15,884,000	3,022,000	(6,034,000)	3,004,000	22,510,000	10,850,000	22,200,000	28,474,000
Annual amortization rate of investment tax credits									3.00%
Current:
Current Deferred Tax (Asset) Liability - Net	10,812,000				(12,779,000)				10,812,000	(12,779,000)
Noncurrent:
Noncurrent Deferred Tax Liability - Net	289,489,000				295,434,000				289,489,000	295,434,000
Accrued interest and penalties on unrecognized tax benefits	600,000				700,000				600,000	700,000	700,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1,				736,000				793,000	736,000	793,000	1,098,000
Increase as a result of tax positions taken in prior years									108,000	119,000	0
Decrease due to a lapse in the statute of limitations									(341,000)	(90,000)	(85,000)
Settlements									0	(86,000)	(220,000)
Balance at December 31,	503,000				736,000				503,000	736,000	793,000
Internal Revenue Service (IRS) [Member]
Noncurrent:
Operating loss carryforwards	215,000,000								215,000,000
Tax credit carryforwards	70,000,000								70,000,000
Alternative minimum tax credits	1,200,000								1,200,000
Internal Revenue Service (IRS) [Member] | 2030 [Member]
Noncurrent:
Tax credit carryforwards	11,600,000								11,600,000
Internal Revenue Service (IRS) [Member] | 2031 [Member]
Noncurrent:
Operating loss carryforwards	171,000,000								171,000,000
Tax credit carryforwards	26,600,000								26,600,000
Internal Revenue Service (IRS) [Member] | 2032 [Member]
Noncurrent:
Operating loss carryforwards	44,000,000								44,000,000
Tax credit carryforwards	32,100,000								32,100,000
State and Local Jurisdiction [Member]
Noncurrent:
Operating loss carryforwards	113,000,000								113,000,000
Alternative minimum tax credits	1,300,000								1,300,000
State and Local Jurisdiction [Member] | 2031 [Member]
Noncurrent:
Operating loss carryforwards	69,000,000								69,000,000
State and Local Jurisdiction [Member] | 2032 [Member]
Noncurrent:
Operating loss carryforwards	44,000,000								44,000,000
Classified as Current [Member]
Current:
Net Operating Loss Carryforward	(2,586,000)				(14,900,000)				(2,586,000)	(14,900,000)
Derivatives / Unrealized Gain	257,000				2,187,000				257,000	2,187,000
Conservation Incentive Program	13,942,000				5,975,000				13,942,000	5,975,000
Budget Billing - Customer Accounts	1,033,000				(4,261,000)				1,033,000	(4,261,000)
Provision for Uncollectibles	(1,883,000)				(1,554,000)				(1,883,000)	(1,554,000)
Other	49,000				(226,000)				49,000	(226,000)
Noncurrent:
Derivatives / Unrealized Gain	257,000				2,187,000				257,000	2,187,000
Net Operating Loss Carryforward	(2,586,000)				(14,900,000)				(2,586,000)	(14,900,000)
Classified as Noncurrent [Member]
Current:
Net Operating Loss Carryforward	(79,217,000)				(65,594,000)				(79,217,000)	(65,594,000)
Derivatives / Unrealized Gain	(82,000)				(2,051,000)				(82,000)	(2,051,000)
Noncurrent:
Book versus Tax Basis of Property	395,322,000				338,472,000				395,322,000	338,472,000
Deferred Gas Costs - Net	3,325,000				12,005,000				3,325,000	12,005,000
Environmental	16,006,000				18,410,000				16,006,000	18,410,000
Deferred Regulatory Costs	15,374,000				7,397,000				15,374,000	7,397,000
Deferred State Tax	(17,924,000)				(14,250,000)				(17,924,000)	(14,250,000)
Investment Tax Credit Basis Gross-Up	(318,000)				(466,000)				(318,000)	(466,000)
Deferred Pension & Other Post Retirement Benefits	39,174,000				36,048,000				39,174,000	36,048,000
Pension & Other Post Retirement Benefits	(33,739,000)				(30,664,000)				(33,739,000)	(30,664,000)
Deferred Revenues	(9,367,000)				(8,073,000)				(9,367,000)	(8,073,000)
Derivatives / Unrealized Gain	(82,000)				(2,051,000)				(82,000)	(2,051,000)
Net Operating Loss Carryforward	(79,217,000)				(65,594,000)				(79,217,000)	(65,594,000)
Investment and Other Tax Credits	(71,547,000)				(26,820,000)				(71,547,000)	(26,820,000)
Equity In Loss Of Affiliated Companies	30,707,000				28,899,000				30,707,000	28,899,000
Other	$ 1,775,000				$ 2,121,000				$ 1,775,000	$ 2,121,000