LONG-TERM DEBT (Details) (USD $)																																																																											1 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2013, 4.46% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2013, 4.46% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2013, 5.027% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2013, 5.027% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2014, 4.52% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2014, 4.52% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2014, 5.115% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2014, 5.115% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2015, 5.387% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2015, 5.387% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2016, 5.437% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2016, 5.437% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2016, 4.6% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2016, 4.6% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2017, 4.657% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2017, 4.657% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2018, 7.97% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2018, 7.97% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2018, 7.125% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2018, 7.125% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2019, 5.587% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2019, 5.587% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2024, 3.00% [Member]		Sep. 30, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2024, 3.00% [Member]	Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2024, 3.00% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2024, 3.03% [Member]		Sep. 30, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2024, 3.03% [Member]	Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2024, 3.03% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2025, 3.63% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2025, 3.63% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2026, 4.84% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2026, 4.84% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2026, 4.93% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2026, 4.93% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2027, 4.03% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2027, 4.03% [Member]		Feb. 28, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2027, 7.7% [Member]	Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2027, 7.7% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2027, 7.7% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2032, 3.74% [Member]		Apr. 30, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2032, 3.74% [Member]	Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2032, 3.74% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2033, 5.55% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2033, 5.55% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2034, 6.213% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2034, 6.213% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2035, 5.45% [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] First Mortgage Bonds [Member] Series Due 2035, 5.45% [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] Bonds at variable rates [Member]		Dec. 31, 2011 South Jersey Gas Company [Member] Bonds at variable rates [Member]		Dec. 31, 2012 South Jersey Gas Company [Member] Bonds at variable rates [Member] Series A. 2006 Bonds [Member]	Dec. 31, 2012 South Jersey Gas Company [Member] Medium-term Notes [Member] Series Due 2027, 7.7% [Member]	Dec. 31, 2011 South Jersey Gas Company [Member] Medium-term Notes [Member] Series Due 2027, 7.7% [Member]	Dec. 31, 2012 Marina Energy LLC [Member] Bonds at variable rates [Member]	Dec. 31, 2012 Marina Energy LLC [Member] Bonds at variable rates [Member] Series A. 2031 Bonds [Member]		Dec. 31, 2011 Marina Energy LLC [Member] Bonds at variable rates [Member] Series A. 2031 Bonds [Member]		Dec. 31, 2012 Marina Energy LLC [Member] Bonds at variable rates [Member] Series B. 2021 Bonds [Member]		Dec. 31, 2011 Marina Energy LLC [Member] Bonds at variable rates [Member] Series B. 2021 Bonds [Member]		Dec. 31, 2012 Marina Energy LLC [Member] Bonds at variable rates [Member] Series A. 2036 [Member]		Dec. 31, 2011 Marina Energy LLC [Member] Bonds at variable rates [Member] Series A. 2036 [Member]		Jun. 30, 2012 South Jersey Industries Inc [Member] Senior Notes [Member]	Dec. 31, 2012 South Jersey Industries Inc [Member] Senior Notes [Member] Series A Notes Due 2015, 2.39% [Member]		Jun. 30, 2012 South Jersey Industries Inc [Member] Senior Notes [Member] Series A Notes Due 2015, 2.39% [Member]	Dec. 31, 2011 South Jersey Industries Inc [Member] Senior Notes [Member] Series A Notes Due 2015, 2.39% [Member]		Dec. 31, 2012 South Jersey Industries Inc [Member] Senior Notes [Member] Series B Notes Due 2017, 2.71% [Member]		Jun. 30, 2012 South Jersey Industries Inc [Member] Senior Notes [Member] Series B Notes Due 2017, 2.71% [Member]	Dec. 31, 2011 South Jersey Industries Inc [Member] Senior Notes [Member] Series B Notes Due 2017, 2.71% [Member]		Dec. 31, 2012 South Jersey Industries Inc [Member] Senior Notes [Member] Series C Notes Due 2022, 3.46% [Member]		Jun. 30, 2012 South Jersey Industries Inc [Member] Senior Notes [Member] Series C Notes Due 2022, 3.46% [Member]	Dec. 31, 2011 South Jersey Industries Inc [Member] Senior Notes [Member] Series C Notes Due 2022, 3.46% [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					4.46%				5.027%				4.52%				5.115%				5.387%				5.437%				4.60%				4.657%				7.97%				7.125%				5.587%				3.00%		3.00%			3.03%		3.03%			3.63%				4.84%				4.93%				4.03%				7.70%	7.70%				3.74%		3.70%			5.55%				6.213%				5.45%																									2.39%		2.39%			2.71%		2.71%			3.46%		3.46%
Long-Term Debt	$ 626,400,000	[1]	$ 426,400,000	[1]	$ 10,500,000	[1],[2]	$ 10,500,000	[1],[2]	$ 14,500,000	[1],[2]	$ 14,500,000	[1],[2]	$ 11,000,000	[1],[2]	$ 11,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 17,000,000	[1],[2]	$ 17,000,000	[1],[2]	$ 15,000,000	[1],[2]	$ 15,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 20,000,000	[1],[2]	$ 20,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 50,000,000	[1],[2],[3]		$ 0	[1],[2],[3]	$ 35,000,000	[1],[2],[3]		$ 0	[1],[2],[3]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 15,000,000	[1],[2]	$ 15,000,000	[1],[2]	$ 45,000,000	[1],[2]	$ 45,000,000	[1],[2]	$ 45,000,000	[1],[2]	$ 45,000,000	[1],[2]		$ 0	[1],[2],[4]	$ 35,000,000	[1],[2],[4]	$ 35,000,000	[1],[2],[4]		$ 0	[1],[2],[4]	$ 32,000,000	[1],[2]	$ 32,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 10,000,000	[1],[2]	$ 25,000,000	[1],[5]	$ 25,000,000	[1],[5]				$ 61,400,000	$ 20,000,000	[1],[6]	$ 20,000,000	[1],[6]	$ 25,000,000	[1],[6]	$ 25,000,000	[1],[6]	$ 16,400,000	[1],[6]	$ 16,400,000	[1],[6]		$ 64,000,000	[1],[7]		$ 0	[1],[7]	$ 16,000,000	[1],[7]		$ 0	[1],[7]	$ 35,000,000	[1],[7]		$ 0	[1],[7]
Less Current Maturities	(25,000,000)	[1]	(2,187,000)	[1]
Total Long-Term Debt	601,400,000	[1]	424,213,000	[1]
Long-term Debt, Fiscal Year Maturity [Abstract]
2013	25,000,000
2014	21,000,000
2015	74,909,000
2016	27,909,000
2017	31,909,000
Debt Instrument, Premium																																																																											2.00%
Debt Instrument, Interest Rate at Period End																																																																																																					0.17%				0.14%				0.24%				0.14%
Long Term Debt, Outstanding Amount Not Fixed By Interest Rate Derivatives																																																																																																								27,100,000
Derivative, Fixed Interest Rate																																																																																																								4.41%
Debt Instrument, Face Amount																																																			50,000,000					35,000,000																			35,000,000							35,000,000																																			115,000,000			64,000,000					16,000,000					35,000,000
Debt Instrument, Maximum Borrowing Capacity																																																																																																							200,000,000
Debt Instrument, Unused Borrowing Capacity, Amount																																																																																																						$ 80,000,000

[1] Long-term debt maturities and sinking funds requirements for the succeeding five years are as follows (in thousands): 2013, $25,000; 2014, $21,000; 2015, $74,909; 2016, $27,909; 2017, $31,909.

[2] The First Mortgage dated October 1, 1947, as supplemented, securing the First Mortgage Bonds constitutes a direct first mortgage lien on substantially all utility plant.

[3] In September 2012, SJG issued $50.0 million of 3.00% aggregate principal amount of MTN's due September 2024. In November 2012, SJG issued $35.0 million of 3.03% aggregate principal amount of MTN's due November 2024.

[4] In February 2012, SJG called its $35.0 million, 7.70% MTN's due April 2027 at par plus a 2.0% premium. The early redemption occurred concurrently with the issuance in April 2012 of $35.0 million, 3.74% Series D MTN's due April 2032.

[5] These variable rate demand bonds bear interest at a floating rate that resets weekly. The interest rate as of December 31, 2012 was 0.17%. Liquidity support on these bonds is provided under a separate letter of credit facility that expires in August, 2015. These bonds contain no financial covenants.

[6] Marina has issued $61.4 million of unsecured variable-rate revenue bonds through the New Jersey Economic Development Authority (NJEDA). The variable rates at December 31, 2012 for the Series A 2001, Series B 2001, and Series A 2006 bonds were 0.14%, 0.24% and 0.14% respectively. The interest rate on all but $27.1 million of the bonds has been effectively fixed via interest rate swaps at 4.41% until January 2026. These bonds contain no financial covenants. Liquidity support on these bonds is provided under a letter of credit facility from a commercial bank that expires in August, 2015.

[7] In June 2012, the Company issued $115.0 million aggregate principal amount of long-term debt, consisting of the following: (a) $64.0 million aggregate principal amount of 2.39% Senior Notes due June 2015; (b) $16.0 million aggregate principal amount of 2.71% Senior Notes due June 2017; and (c) $35.0 million aggregate principal amount of 3.46% Senior Notes due June 2022.