PENSION AND OTHER POSTRETIREMENT BENEFITS 4 (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Amounts Recognized in the Statement of Financial Position Consist of [Abstract]
Current Liabilities	$ (1,236,000)	$ (1,240,000)
Noncurrent Liabilities	(89,193,000)	(90,055,000)
Pension Benefits [Member]
Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning of Year	160,319,000	138,132,000
Service Cost	3,718,000	3,048,000	2,648,000
Interest Cost	8,008,000	7,828,000	7,584,000
Actuarial Loss	21,990,000	18,259,000
Retiree Contributions	0	0
Plan Amendments	0	0
Benefits Paid	(7,136,000)	(6,948,000)
Benefit Obligation, Ending of Year	186,899,000	160,319,000	138,132,000
Change in Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	91,738,000	95,746,000
Actual Return on Plan Assets	13,853,000	1,755,000
Employer Contributions	20,936,000	1,185,000
Retiree Contributions	0	0
Benefits Paid	(7,136,000)	(6,948,000)
Fair Value of Plan Assets at End of Year	119,391,000	91,738,000	95,746,000
Amounts Recognized in the Statement of Financial Position Consist of [Abstract]
Current Liabilities	(1,236,000)	(1,240,000)
Noncurrent Liabilities	(66,272,000)	(67,341,000)
Net Amount Recognized at End of Year	(67,508,000)	(68,581,000)
Amounts Recognized in Regulatory Assets Consist of [Abstract]
Prior Service Costs (Credit)	842,000	1,049,000
Net Actuarial Loss	67,871,000	60,762,000
Amount Recognized in Regulatory Assets	68,713,000	61,811,000	47,197,000
Amounts Recognized in Accumulated Other Comprehensive Loss [Abstract]
Net Actuarial Loss	21,908,000	19,061,000
Projected benefit obligation	149,500,000	128,800,000
Accumulated benefit obligation	135,600,000	117,000,000
Other Postretirement Benefits [Member]
Change in Benefit Obligation [Roll Forward]
Benefit Obligation, Beginning of Year	51,656,000	47,695,000
Service Cost	704,000	675,000	644,000
Interest Cost	2,443,000	2,621,000	2,708,000
Actuarial Loss	4,059,000	3,666,000
Retiree Contributions	313,000	347,000
Plan Amendments	0	524,000
Benefits Paid	(3,560,000)	(3,872,000)
Benefit Obligation, Ending of Year	55,615,000	51,656,000	47,695,000
Change in Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	28,942,000	29,145,000
Actual Return on Plan Assets	3,880,000	(353,000)
Employer Contributions	3,119,000	3,675,000
Retiree Contributions	313,000	347,000
Benefits Paid	(3,560,000)	(3,872,000)
Fair Value of Plan Assets at End of Year	32,694,000	28,942,000	29,145,000
Amounts Recognized in the Statement of Financial Position Consist of [Abstract]
Current Liabilities	0	0
Noncurrent Liabilities	(22,921,000)	(22,714,000)
Net Amount Recognized at End of Year	(22,921,000)	(22,714,000)
Amounts Recognized in Regulatory Assets Consist of [Abstract]
Prior Service Costs (Credit)	758,000	563,000
Net Actuarial Loss	26,426,000	25,872,000
Amount Recognized in Regulatory Assets	27,184,000	26,435,000	21,064,000
Amounts Recognized in Accumulated Other Comprehensive Loss [Abstract]
Net Actuarial Loss	0	0
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Amounts Recognized in Accumulated Other Comprehensive Loss [Abstract]
Projected benefit obligation	37,400,000	31,500,000
Accumulated benefit obligation	35,700,000	29,200,000
SJI [Member] | Pension Benefits [Member]
Change in Plan Assets [Roll Forward]
Funded Status at End of Year:	(67,508,000)	(68,581,000)
SJI [Member] | Other Postretirement Benefits [Member]
Change in Plan Assets [Roll Forward]
Funded Status at End of Year:	$ (22,921,000)	$ (22,714,000)