LONG-TERM DEBT (Details)	1 Months Ended		12 Months Ended
	Nov. 30, 2019 USD ($)	Apr. 30, 2018 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Nov. 10, 2020 USD ($) tranche	Oct. 01, 2020	May 27, 2020 USD ($) tranche	Apr. 30, 2020 USD ($) tranche	Dec. 31, 2018 USD ($)	Oct. 31, 2018 USD ($) bank
Debt Instrument [Line Items]
Stated interest rate (as a percent)			7.50%	7.50%
Total Long-Term Debt Outstanding			$ 2,950,946,000	$ 2,568,855,000
Less Current Maturities			(142,801,000)	(467,909,000)
Total Long-Term Debt			2,808,145,000	2,100,946,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2021			142,801,000
2022			66,084,000
2023			40,084,000
2024			65,084,000
2025			66,084,000
Long-term debt outstanding			2,950,946,000	2,568,855,000
Long-term debt, current			142,801,000	467,909,000
Debt discount			5,200,000	5,300,000
Unamortized debt issuance costs			29,600,000	25,500,000
Finance lease, lease liability			$ 3,053,000	$ 0
Covenant, indebtedness to capitalization maximum			0.70
Junior Subordinated Notes due 2079, 5.626 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)				5.625%
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal amount issued				$ 200,000,000.0
Debt discount				5,300,000
Net cash proceeds from issuance of debt				194,700,000
South Jersey Gas Company
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding			$ 1,078,446,000	971,355,000
Less Current Maturities			(52,809,000)	(417,909,000)
Total Long-Term Debt			1,025,637,000	553,446,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2021			52,809,000
2022			31,084,000
2023			40,084,000
2024			40,084,000
2025			41,084,000
Long-term debt outstanding			1,078,446,000	971,355,000
Long-term debt, current			52,809,000	417,909,000
Unamortized debt issuance costs			$ 9,400,000	6,300,000
South Jersey Gas Company | Credit Agreement | Unsecured term loan
Long-term Debt, Fiscal Year Maturity [Abstract]
Amount of facility										$ 400,000,000.0
Number of banks | bank										8
South Jersey Gas Company | First Mortgage Bonds | Series due 2030, 3.28 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.28%
Total Long-Term Debt Outstanding			$ 150,000,000	0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 150,000,000	0
South Jersey Gas Company | First Mortgage Bonds | Series due 2050, 3.93 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.93%
Total Long-Term Debt Outstanding			$ 250,000,000	0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 250,000,000	0
South Jersey Gas Company | First Mortgage Bonds | Series due 2050, 3.98 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.98%
Total Long-Term Debt Outstanding			$ 125,000,000	0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 125,000,000	0
South Jersey Gas Company | First Mortgage Bonds | Series due 2024, 3.00 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.00%
Total Long-Term Debt Outstanding			$ 40,000,000	50,000,000
Less Current Maturities			(10,000,000.0)
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			40,000,000	50,000,000
Annual payment			10,000,000.0
Long-term debt, current			$ 10,000,000.0
South Jersey Gas Company | First Mortgage Bonds | Series due 2024, 3.03 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.03%
Total Long-Term Debt Outstanding			$ 28,000,000	35,000,000
Less Current Maturities			(7,000,000.0)
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			28,000,000	35,000,000
Annual payment			7,000,000.0
Long-term debt, current			$ 7,000,000.0
South Jersey Gas Company | First Mortgage Bonds | Series due 2025, 3.63 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.63%
Total Long-Term Debt Outstanding			$ 4,546,000	5,455,000
Less Current Maturities			(900,000)
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			4,546,000	5,455,000
Long-term debt, current			900,000
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 (as a percent)			4.84%
Total Long-Term Debt Outstanding			$ 15,000,000	15,000,000
Less Current Maturities			(2,500,000)
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			15,000,000	15,000,000
Annual payment			2,500,000
Long-term debt, current			$ 2,500,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2026, 4.93 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.93%
Total Long-Term Debt Outstanding			$ 45,000,000	45,000,000
Less Current Maturities			(7,500,000)
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			45,000,000	45,000,000
Annual payment			7,500,000
Long-term debt, current			$ 7,500,000
South Jersey Gas Company | First Mortgage Bonds | Series due 2027, 4.03 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.03%
Total Long-Term Debt Outstanding			$ 45,000,000	45,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
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 (as a percent)			4.01%
Total Long-Term Debt Outstanding			$ 34,000,000	34,000,000					$ 42,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 34,000,000	34,000,000					$ 42,000,000.0
South Jersey Gas Company | First Mortgage Bonds | Series due 2030, 4.23 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.23%
Total Long-Term Debt Outstanding			$ 30,000,000	30,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
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 (as a percent)			3.74%
Total Long-Term Debt Outstanding			$ 35,000,000.0	35,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			35,000,000.0	35,000,000
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 (as a percent)			5.55%
Total Long-Term Debt Outstanding			$ 32,000,000	32,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
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 (as a percent)			6.213%
Total Long-Term Debt Outstanding			$ 10,000,000	10,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
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 (as a percent)			5.45%
Total Long-Term Debt Outstanding			$ 10,000,000	10,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
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 (as a percent)			3.00%
Total Long-Term Debt Outstanding			$ 200,000,000	200,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			200,000,000	200,000,000
Annual payment			$ 16,000,000.0
South Jersey Gas Company | First Mortgage Bonds | Series Due 2023, 4.03 Percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.03%
Total Long-Term Debt Outstanding			$ 45,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			45,000,000.0
Annual payment			9,000,000.0
South Jersey Gas Company | First Mortgage Bonds | Medium-Term Note, 4.01%, Due November 2018 and November 2019
Long-term Debt, Fiscal Year Maturity [Abstract]
Repayments of senior debt	$ 8,000,000.0
South Jersey Gas Company | First Mortgage Bonds | Medium-Term Note, 4.01%, Due November 2025
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding			2,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			2,000,000.0
South Jersey Gas Company | First Mortgage Bonds | Medium-Term Note, 4.01%, Due November 2026
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding			3,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			3,000,000.0
South Jersey Gas Company | First Mortgage Bonds | Medium-Term Note, 4.01%, Due November 2027
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding			8,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			8,000,000.0
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			7,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			7,000,000.0
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]
Long-term debt outstanding			$ 24,900,000	24,900,000
Interest rate at period end (as a percent)			0.09%
South Jersey Gas Company | Loans payable | Unsecured term loan
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding			$ 0	400,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			0	400,000,000
South Jersey Gas Company | Senior notes | Senior Secured Notes, Series F, 2020
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal amount issued								$ 525,000,000.0
Number of tranches | tranche								3
South Jersey Gas Company | Senior notes | Senior Secured Notes, Series F, 2020 | Tranche A
Debt Instrument [Line Items]
Stated interest rate (as a percent)								3.28%
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal amount issued								$ 150,000,000.0
South Jersey Gas Company | Senior notes | Senior Secured Notes, Series F, 2020 | Tranche B
Debt Instrument [Line Items]
Stated interest rate (as a percent)								3.93%
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal amount issued								$ 250,000,000.0
South Jersey Gas Company | Senior notes | Senior Secured Notes, Series F, 2020 | Tranche C
Debt Instrument [Line Items]
Stated interest rate (as a percent)						3.98%
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal amount issued								$ 125,000,000.0
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			0	50,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 0	50,000,000
South Jersey Industries Inc. | Senior notes | Series due 2027, 3.71 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.71%
Total Long-Term Debt Outstanding			$ 75,000,000	0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 75,000,000	0
South Jersey Industries Inc. | Senior notes | Series due 2027, 3.71 percent | Tranche A
Debt Instrument [Line Items]
Stated interest rate (as a percent)							3.71%
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal amount issued							$ 75,000,000.0
South Jersey Industries Inc. | Senior notes | Series due 2030, 3.91 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.91%
Total Long-Term Debt Outstanding			$ 125,000,000	0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 125,000,000	0
South Jersey Industries Inc. | Senior notes | Series due 2030, 3.91 percent | Tranche B
Debt Instrument [Line Items]
Stated interest rate (as a percent)							3.91%
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal amount issued							$ 125,000,000.0
South Jersey Industries Inc. | Senior notes | Series C 2012 Notes due 2022, 3.71 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.71%
Total Long-Term Debt Outstanding			$ 35,000,000	35,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
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 (as a percent)			3.47%
Total Long-Term Debt Outstanding			$ 25,000,000	25,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
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 (as a percent)			3.71%
Total Long-Term Debt Outstanding			$ 25,000,000	25,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
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 (as a percent)			3.57%
Total Long-Term Debt Outstanding			$ 25,000,000	25,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 25,000,000	25,000,000
South Jersey Industries Inc. | Senior notes | Series 2017B-2 due 2028, 3.81 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.81%
Total Long-Term Debt Outstanding			$ 25,000,000	25,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 25,000,000	25,000,000
South Jersey Industries Inc. | Senior notes | Series 2018A due 2021, 3.42 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.43%
Total Long-Term Debt Outstanding			$ 90,000,000	90,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 90,000,000	90,000,000
South Jersey Industries Inc. | Senior notes | Series 2018B due 2028, 4.07 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.07%
Total Long-Term Debt Outstanding			$ 80,000,000	80,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 80,000,000	80,000,000
South Jersey Industries Inc. | Senior notes | Series 2018C due 2030, 4.17 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.17%
Total Long-Term Debt Outstanding			$ 80,000,000	80,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 80,000,000	80,000,000
South Jersey Industries Inc. | Senior notes | Junior Subordinated Notes due 2079, 5.626 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			5.625%
Total Long-Term Debt Outstanding			$ 200,000,000	200,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			200,000,000	200,000,000
South Jersey Industries Inc. | Senior notes | Convertible Equity Units
Debt Instrument [Line Items]
Total Long-Term Debt Outstanding			287,500,000	287,500,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 287,500,000	287,500,000
South Jersey Industries Inc. | Senior notes | Senior Unsecured Notes
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal amount issued							$ 200,000,000.0
Number of tranches | tranche							2
ETG Utility Operations | First Mortgage Bonds | Series 2018A-1 due 2028, 4.02 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.02%
Total Long-Term Debt Outstanding			$ 50,000,000	50,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 50,000,000	50,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2018A-2 due 2033, 4.22 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.22%
Total Long-Term Debt Outstanding			$ 55,000,000	55,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 55,000,000	55,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2018A-3 due 2038, 4.29 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.29%
Total Long-Term Debt Outstanding			$ 150,000,000	150,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 150,000,000	150,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2018A-4 due 2048, 4.37 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.37%
Total Long-Term Debt Outstanding			$ 200,000,000	200,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 200,000,000	200,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2018A-5 due 2058, 4.52 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.52%
Total Long-Term Debt Outstanding			$ 75,000,000	75,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 75,000,000	75,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2019A-1 due 2029, 2.84 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			2.84%
Total Long-Term Debt Outstanding			$ 40,000,000	40,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 40,000,000	40,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2019 A-2 due 2029, 2.84 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			2.84%
Total Long-Term Debt Outstanding			$ 35,000,000	35,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 35,000,000	35,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2019 A-3 due 2031, 2.94 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			2.94%
Total Long-Term Debt Outstanding			$ 25,000,000	25,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 25,000,000	25,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2019 A-4 due 2031, 2.94 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			2.94%
Total Long-Term Debt Outstanding			$ 45,000,000	45,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 45,000,000	45,000,000
ETG Utility Operations | First Mortgage Bonds | Series 2020 A-1, Tranche A due 2050, 3.28 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.28%		3.28%
Total Long-Term Debt Outstanding			$ 75,000,000	0	$ 75,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 75,000,000	0	$ 75,000,000.0
ETG Utility Operations | First Mortgage Bonds | Series 2020 A-1, Tranche B due 2060, 3.38 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)			3.38%		3.38%
Total Long-Term Debt Outstanding			$ 50,000,000	0	$ 50,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding			$ 50,000,000	$ 0	50,000,000.0
ETG Utility Operations | First Mortgage Bonds | Bond Purchase Agreement
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal amount issued					$ 250,000,000.0
Number of tranches | tranche					5
ETG Utility Operations | First Mortgage Bonds | Series 2020 A-2, Tranche A due 2031, 2.26 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)					2.26%
Total Long-Term Debt Outstanding					$ 50,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding					$ 50,000,000.0
ETG Utility Operations | First Mortgage Bonds | Series 2020 A-2, Tranche B due 2041, 3.08 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)					3.08%
Total Long-Term Debt Outstanding					$ 25,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding					$ 25,000,000.0
ETG Utility Operations | First Mortgage Bonds | Series 2020 A-2, Tranche C due 2051, 3.36 percent
Debt Instrument [Line Items]
Stated interest rate (as a percent)					3.36%
Total Long-Term Debt Outstanding					$ 50,000,000.0
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt outstanding					$ 50,000,000.0
Capital Units
Long-term Debt, Fiscal Year Maturity [Abstract]
Sale of stock, equity units		$ 287,500,000