LONG-TERM DEBT (Details)			1 Months Ended		12 Months Ended
	Jul. 01, 2018	Jun. 26, 2018 USD ($)	Jul. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) Tranche	Oct. 31, 2018 USD ($) bank	Dec. 31, 2017 USD ($)	Jan. 31, 2017 USD ($)
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					$ 2,867,764,000		$ 1,204,173,000
Less SJI Consolidated Current Maturities					(733,909,000)		(63,809,000)
Total Long-Term Debt					2,133,855,000		1,140,364,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2019					733,909,000
2020					377,909,000
2021					405,409,000
2022					66,084,000
2023					40,084,000
Amount of facility					860,000,000
Unamortized debt issuance costs					27,000,000		17,400,000
Term loan
Long-term Debt, Fiscal Year Maturity [Abstract]
Private placement		$ 530,000,000			$ 530,000,000.0
Term of agreement		364 days			364 days
Senior notes | Series Notes at variable rates due 2019
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate at period end					4.38%
South Jersey Gas Company
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					$ 900,264,000		829,173,000
Less SJI Consolidated Current Maturities					(18,909,000)		(63,809,000)
Total Long-Term Debt					881,355,000		765,364,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2019					18,909,000
2020					327,909,000
2021					27,909,000
2022					31,084,000
2023					40,084,000
Amount of facility					210,000,000
Unamortized debt issuance costs					6,800,000		7,300,000
South Jersey Gas Company | Term facility
Long-term Debt, Fiscal Year Maturity [Abstract]
Amount of facility					10,000,000
South Jersey Gas Company | Unsecured term loan
Long-term Debt, Fiscal Year Maturity [Abstract]
Line of credit balance					$ 200,000,000
South Jersey Gas Company | Maximum borrowing capacity | Unsecured term loan
Long-term Debt, Fiscal Year Maturity [Abstract]
Number of banks | bank						8
Amount of facility						$ 400,000,000.0		$ 200,000,000
South Jersey Gas Company | First Mortgage Bonds | Series Due 2023, 4.03 Percent
Debt Instrument [Line Items]
Stated interest rate					4.03%
Total Long-Term Debt Outstanding					$ 45,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Annual payment					$ 9,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2018, 7.97 percent
Debt Instrument [Line Items]
Stated interest rate			7.97%		7.97%
Total Long-Term Debt Outstanding					$ 0		10,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Amount of debt retired					$ 10,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2018, 7.125 percent
Debt Instrument [Line Items]
Stated interest rate			7.125%		7.125%
Total Long-Term Debt Outstanding					$ 0		20,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Amount of debt retired			$ 20,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2019, 5.587 percent
Debt Instrument [Line Items]
Stated interest rate					5.587%
Total Long-Term Debt Outstanding					$ 10,000,000		10,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2024, 3.00 percent
Debt Instrument [Line Items]
Stated interest rate					3.00%
Total Long-Term Debt Outstanding					$ 50,000,000		50,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Annual payment					$ 10,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2024, 3.03 percent
Debt Instrument [Line Items]
Stated interest rate					3.03%
Total Long-Term Debt Outstanding					$ 35,000,000		35,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Annual payment					$ 7,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2025, 3.63 percent
Debt Instrument [Line Items]
Stated interest rate					3.63%
Total Long-Term Debt Outstanding					$ 6,364,000		7,273,000
Less SJI Consolidated Current Maturities					(900,000)
Long-term Debt, Fiscal Year Maturity [Abstract]
Payment towards principal					$ 900,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2026, 4.84 percent
Debt Instrument [Line Items]
Stated interest rate					4.84%
Total Long-Term Debt Outstanding					$ 15,000,000		15,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Annual payment					$ 2,500,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2026, 4.93 percent
Debt Instrument [Line Items]
Stated interest rate					4.93%
Total Long-Term Debt Outstanding					$ 45,000,000		45,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Annual payment					$ 7,500,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2027, 4.03 percent
Debt Instrument [Line Items]
Stated interest rate					4.03%
Total Long-Term Debt Outstanding					$ 45,000,000		45,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2030, 4.01 percent
Debt Instrument [Line Items]
Stated interest rate					4.01%
Total Long-Term Debt Outstanding					$ 42,000,000		50,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2030, 4.23 percent
Debt Instrument [Line Items]
Stated interest rate					4.23%
Total Long-Term Debt Outstanding					$ 30,000,000		30,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2032, 3.74 percent
Debt Instrument [Line Items]
Stated interest rate					3.74%
Total Long-Term Debt Outstanding					$ 35,000,000		35,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Annual payment					$ 3,175,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2033, 5.55 percent
Debt Instrument [Line Items]
Stated interest rate					5.55%
Total Long-Term Debt Outstanding					$ 32,000,000		32,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2034, 6.213 percent
Debt Instrument [Line Items]
Stated interest rate					6.213%
Total Long-Term Debt Outstanding					$ 10,000,000		10,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2035, 5.45 percent
Debt Instrument [Line Items]
Stated interest rate					5.45%
Total Long-Term Debt Outstanding					$ 10,000,000		10,000,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2047, 3.00 percent
Debt Instrument [Line Items]
Stated interest rate					3.00%
Total Long-Term Debt Outstanding					$ 200,000,000		200,000,000
South Jersey Gas Company | First Mortgage Bonds | Medium-Term Note, 4.01%, Due November 2018 and November 2019
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					8,000,000
South Jersey Gas Company | First Mortgage Bonds | Medium-Term Note, 4.01%, Due November 2025
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					2,000,000
South Jersey Gas Company | First Mortgage Bonds | Medium-Term Note, 4.01%, Due November 2026
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					3,000,000
South Jersey Gas Company | First Mortgage Bonds | Medium-Term Note, 4.01%, Due November 2027
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					8,000,000
South Jersey Gas Company | First Mortgage Bonds | Medium-Term Note, 4.01%, Due November 2028, November 2029 and November 2030
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					7,000,000
South Jersey Gas Company | Unsecured debt | Series A 2006 Bonds at variable rates due 2036
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					$ 24,900,000		24,900,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate at period end					1.78%
South Jersey Gas Company | Loans payable | Unsecured term loan
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					$ 310,000,000		0
South Jersey Gas Company | Loans payable | Term facility
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					$ 0		200,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2018A-1 due 2028, 4.02 percent
Debt Instrument [Line Items]
Stated interest rate					4.02%
Total Long-Term Debt Outstanding					$ 50,000,000		0
ETG Utility Operations | First Mortgage Bonds | Series 2018A-2 due 2033, 4.22 percent
Debt Instrument [Line Items]
Stated interest rate					4.22%
Total Long-Term Debt Outstanding					$ 55,000,000		0
ETG Utility Operations | First Mortgage Bonds | Series 2018A-3 due 2038, 4.29 percent
Debt Instrument [Line Items]
Stated interest rate					4.29%
Total Long-Term Debt Outstanding					$ 150,000,000		0
ETG Utility Operations | First Mortgage Bonds | Series 2018A-4 due 2048, 4.37 percent
Debt Instrument [Line Items]
Stated interest rate					4.37%
Total Long-Term Debt Outstanding					$ 200,000,000		0
ETG Utility Operations | First Mortgage Bonds | Series 2018A-5 due 2058, 4.52 percent
Debt Instrument [Line Items]
Stated interest rate					4.52%
Total Long-Term Debt Outstanding					$ 75,000,000		0
ETG Utility Operations | First Mortgage Bonds | Series 2018A
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					$ 530,000,000
Long Term Debt, Number of Tranches | Tranche					5
South Jersey Industries Inc.
Long-term Debt, Fiscal Year Maturity [Abstract]
Amount of facility					$ 450,000,000
South Jersey Industries Inc. | Unsecured debt | South Jersey Industries Term Loan at variable rates due 2020
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					$ 50,000,000		50,000,000
South Jersey Industries Inc. | Unsecured debt | South Jersey Industries Term Loan at variable rates due 2020 | Term facility
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate at period end					3.67%
South Jersey Industries Inc. | Senior notes
Debt Instrument [Line Items]
Long Term Debt, Interest Rate Increase	25.00%
South Jersey Industries Inc. | Senior notes | Series due 2019, 3.30 percent
Debt Instrument [Line Items]
Stated interest rate					3.30%
Total Long-Term Debt Outstanding					$ 60,000,000		60,000,000
South Jersey Industries Inc. | Senior notes | Series due 2019, 3.30 percent
Debt Instrument [Line Items]
Stated interest rate					3.30%
Total Long-Term Debt Outstanding					$ 30,000,000		30,000,000
South Jersey Industries Inc. | Senior notes | Series due 2019, 3.30 percent
Debt Instrument [Line Items]
Stated interest rate					3.30%
Total Long-Term Debt Outstanding					$ 50,000,000		50,000,000
South Jersey Industries Inc. | Senior notes | Series C 2012 Notes due 2022, 3.71 percent
Debt Instrument [Line Items]
Stated interest rate					3.71%
Total Long-Term Debt Outstanding					$ 35,000,000		35,000,000
South Jersey Industries Inc. | Senior notes | Series due 2024, 3.47 percent
Debt Instrument [Line Items]
Stated interest rate					3.47%
Total Long-Term Debt Outstanding					$ 25,000,000		25,000,000
South Jersey Industries Inc. | Senior notes | Series due 2027, 3.71 percent
Debt Instrument [Line Items]
Stated interest rate					3.71%
Total Long-Term Debt Outstanding					$ 25,000,000		25,000,000
South Jersey Industries Inc. | Senior notes | Series 2017A-2 due 2025, 3.57 percent
Debt Instrument [Line Items]
Stated interest rate					3.57%
Total Long-Term Debt Outstanding					$ 25,000,000		0
South Jersey Industries Inc. | Senior notes | Series 2017B-2 due 2028, 3.81 percent
Debt Instrument [Line Items]
Stated interest rate					3.81%
Total Long-Term Debt Outstanding					$ 25,000,000		0
South Jersey Industries Inc. | Senior notes | Series 2018A due 2021, 3.42 percent
Debt Instrument [Line Items]
Stated interest rate					3.43%
Total Long-Term Debt Outstanding					$ 90,000,000		0
South Jersey Industries Inc. | Senior notes | Series 2018B due 2028, 4.07 percent
Debt Instrument [Line Items]
Stated interest rate					4.07%
Total Long-Term Debt Outstanding					$ 80,000,000		0
South Jersey Industries Inc. | Senior notes | Series 2018C due 2030, 4.17 percent
Debt Instrument [Line Items]
Stated interest rate					4.17%
Total Long-Term Debt Outstanding					$ 80,000,000		0
South Jersey Industries Inc. | Senior notes | Series Notes at variable rates due 2019
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					40,000,000		40,000,000
South Jersey Industries Inc. | Senior notes | Series Notes at variable rates due 2019
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					60,000,000		60,000,000
South Jersey Industries Inc. | Senior notes | Convertible Equity Units
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					287,500,000		0
South Jersey Industries Inc. | Senior notes | Series 2018D Notes at variable rates due 2019
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding					$ 475,000,000		$ 0
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate at period end					3.76%
Capital Units
Long-term Debt, Fiscal Year Maturity [Abstract]
Sale of stock, equity units				$ 287,500,000