INCOME TAXES AND CREDITS (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at Statutory Rate									$ 33,974,000	$ 32,183,000	$ 30,510,000
Increase (Decrease) Resulting from:
State Income Taxes									4,833,000	5,302,000	5,316,000
Amortization of Investment Tax Credits									(258,000)	(287,000)	(302,000)
ESOP Dividend									(1,058,000)	(1,027,000)	(956,000)
AFUDC									(916,000)	(1,048,000)	(729,000)
Amortization of Flowthrough Depreciation									0	0	526,000
Other - Net									(1,742,000)	(1,412,000)	(84,000)
Net Income Taxes	11,322,000	471,000	2,269,000	20,771,000	10,589,000	258,000	1,887,000	20,977,000	34,833,000	33,711,000	34,281,000
Current:
Federal									(53,000)	(4,635,000)	(924,000)
State									2,946,000	(7,000)	168,000
Total Current									2,893,000	(4,642,000)	(756,000)
Deferred:
Federal									27,707,000	30,477,000	27,329,000
State									4,491,000	8,163,000	8,010,000
Total Deferred									32,198,000	38,640,000	35,339,000
Investment Tax Credits									(258,000)	(287,000)	(302,000)
Net Income Taxes	11,322,000	471,000	2,269,000	20,771,000	10,589,000	258,000	1,887,000	20,977,000	34,833,000	33,711,000	34,281,000
Annual amortization rate of investment tax credits									3.00%
Current:
Current Deferred Tax (Asset) Liability - Net	(23,309,000)				10,432,000				(23,309,000)	10,432,000
Noncurrent:
Noncurrent Deferred Tax Liability – Net	380,975,000				310,357,000				380,975,000	310,357,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1,				503,000				421,000	503,000	421,000	478,000
Increase as a result of tax position taken in prior years									44,000	82,000	119,000
Decrease due to a lapse in the statue of limitations									0	0	(90,000)
Settlements									0	0	(86,000)
Balance at December 31,	547,000				503,000				547,000	503,000	421,000
Accrued interest and penalties on unrecognized tax benefits	600,000				600,000				600,000	600,000	600,000
Internal Revenue Service (IRS) [Member]
Noncurrent:
Operating loss carryforwards	103,700,000								103,700,000
Internal Revenue Service (IRS) [Member] | 2031 [Member]
Noncurrent:
Operating loss carryforwards	99,400,000								99,400,000
Internal Revenue Service (IRS) [Member] | 2032 [Member]
Noncurrent:
Operating loss carryforwards	4,300,000								4,300,000
SJI [Member] | Prepaid Taxes [Member]
Noncurrent:
Income taxes due from parent company	0				4,600,000				0	4,600,000
Classified as Current [Member]
Current:
Net Operating Loss Carryforward	(27,600,000)				(2,586,000)				(27,600,000)	(2,586,000)
Budget Billing - Customer Accounts	1,152,000				1,033,000				1,152,000	1,033,000
Provision for Uncollectibles	(1,726,000)				(1,409,000)				(1,726,000)	(1,409,000)
Conservation Incentive Program	4,631,000				13,942,000				4,631,000	13,942,000
Section 461 Prepayments	1,156,000				930,000				1,156,000	930,000
Other	(922,000)				(1,478,000)				(922,000)	(1,478,000)
Classified as Noncurrent [Member]
Current:
Net Operating Loss Carryforward	(8,764,000)				(35,901,000)				(8,764,000)	(35,901,000)
Noncurrent:
Book Versus Tax Basis of Property	371,684,000				323,470,000				371,684,000	323,470,000
Deferred Fuel Costs - Net	1,330,000				3,325,000				1,330,000	3,325,000
Environmental Remediation	14,392,000				17,643,000				14,392,000	17,643,000
Deferred Regulatory Costs	13,665,000				15,374,000				13,665,000	15,374,000
Deferred State Tax	(15,471,000)				(15,106,000)				(15,471,000)	(15,106,000)
Investment Tax Credit Basis Gross-Up	(185,000)				(318,000)				(185,000)	(318,000)
Deferred Pension & Other Post Retirement Benefits	24,218,000				39,174,000				24,218,000	39,174,000
Pension & Other Post Retirement Benefits	(14,152,000)				(28,846,000)				(14,152,000)	(28,846,000)
Deferred Revenues	(9,266,000)				(8,922,000)				(9,266,000)	(8,922,000)
Other	$ 3,524,000				$ 464,000				$ 3,524,000	$ 464,000