LONG-TERM DEBT (Details) (USD $)																																																																																																						1 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Jan. 31, 2014 First Mortgage Bonds [Member] Subsequent Event [Member]	Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2013, 4.46% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2013, 4.46% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2013, 5.027% [Member]		Jul. 31, 2013 First Mortgage Bonds [Member] Series Due 2013, 5.027% [Member]	Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2013, 5.027% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2014, 4.52% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2014, 4.52% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2014, 5.115% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2014, 5.115% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2015, 5.387% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2015, 5.387% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2016, 5.437% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2016, 5.437% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2016, 4.60% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2016, 4.60% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2017, 4.657% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2017, 4.657% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2018, 7.97% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2018, 7.97% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2018, 7.125% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2018, 7.125% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2019, 5.587% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2019, 5.587% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2024, 3.00% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2024, 3.00% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2024, 3.03% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2024, 3.03% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2025, 3.63% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2025, 3.63% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2026, 4.84% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2026, 4.84% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2026, 4.93% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2026, 4.93% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2027, 4.03% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2027, 4.03% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2030, 4.01% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2030, 4.01% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2032, 3.74% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2032, 3.74% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2033, 5.55% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2033, 5.55% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2034, 6.213% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2034, 6.213% [Member]		Dec. 31, 2013 First Mortgage Bonds [Member] Series Due 2035, 5.45% [Member]		Dec. 31, 2012 First Mortgage Bonds [Member] Series Due 2035, 5.45% [Member]		Dec. 31, 2013 Bonds at variable rates [Member]		Dec. 31, 2012 Bonds at variable rates [Member]		Dec. 31, 2013 Bonds at variable rates [Member] Series A. 2006 Bonds [Member]	Dec. 31, 2013 Medium-term Notes [Member]	Dec. 31, 2011 Medium-term Notes [Member]	Jul. 31, 2013 Medium-term Notes [Member] Series Due 2013, 4.46% [Member]
Debt Instrument [Line Items]
Stated interest rate					4.23%	4.46%				5.027%		5.027%			4.52%				5.115%				5.387%				5.437%				4.60%				4.657%				7.97%				7.125%				5.587%				3.00%				3.03%				3.63%				4.84%				4.93%				4.03%				4.01%				3.74%				5.55%				6.213%				5.45%											4.46%
Total Long-Term Debt Outstanding	$ 475,000,000	[1]	$ 450,000,000	[1]		$ 0	[1],[2],[3]	$ 10,500,000	[1],[2],[3]	$ 0	[1],[2],[3]	$ 14,500,000	$ 14,500,000	[1],[2],[3]	$ 11,000,000	[1],[3]	$ 11,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 17,000,000	[1],[3]	$ 17,000,000	[1],[3]	$ 15,000,000	[1],[3]	$ 15,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 20,000,000	[1],[3]	$ 20,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 50,000,000	[1],[3]	$ 50,000,000	[1],[3]	$ 35,000,000	[1],[3]	$ 35,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 15,000,000	[1],[3]	$ 15,000,000	[1],[3]	$ 45,000,000	[1],[3]	$ 45,000,000	[1],[3]	$ 45,000,000	[1],[3]	$ 45,000,000	[1],[3]	$ 50,000,000	[1],[3],[4]	$ 0	[1],[3],[4]	$ 35,000,000	[1],[3]	$ 35,000,000	[1],[3]	$ 32,000,000	[1],[3]	$ 32,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 10,000,000	[1],[3]	$ 25,000,000	[1],[5]	$ 25,000,000	[1],[5]
Less Current Maturities	(21,000,000)	[1]	(25,000,000)	[1]
Long-Term Debt	454,000,000	[1]	425,000,000	[1]
Long-term Debt, Fiscal Year Maturity [Abstract]
2014	21,000,000
2015	10,909,000
2016	27,909,000
2017	15,909,000
2018	38,909,000
Extinguishment of Debt, Amount																																																																																																						10,500,000.0
Interest rate at end of period																																																																																																			0.07%
Approved borrowing capacity																																																																																																					200,000,000.0
Available borrowing capacity																																																																																																				30,000,000
Debt Instrument, Face Amount					$ 30,000,000

[1] Long-term debt maturities and sinking funds requirements for the succeeding five years are as follows (in thousands): 2014, $21,000; 2015, $10,909; 2016, $27,909; 2017, $15,909; 2018, $38,909 .Our long-term debt agreements contain no financial covenants.

[2] In July 2013, SJG called its $10.5 million, 4.46% Medium Term Notes (MTN) due July 2013 and $14.5 million, 5.027% MTN due September 2013.

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

[4] In November 2013, SJG issued $50.0 million of 4.01% aggregate principal amount of MTN due November 2030.

[5] These variable rate demand bonds bear interest at a floating rate that resets weekly. The interest rate as of December 31, 2013 was 0.07%. 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.