FAIR VALUE OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / decatherm	Dec. 31, 2016 USD ($) $ / decatherm
Changes in significant unobservable inputs [Roll forward]
Balance at beginning of period	$ 9,035	$ (632)
Other changes in fair value from continuing and new contracts, net	1,857	5,657
Transfers in to/(out of) of Level 3	(954)
Transfers in to/(out of) of Level 3 (A)		4,116
Settlements	(6,828)	(106)
Balance at end of period	$ 3,110	$ 9,035
Level 3 | Forward Contract | Minimum
Liabilities
Forward price (in USD per dt) | $ / decatherm	1.79	1.03
Level 3 | Forward Contract | Maximum
Liabilities
Forward price (in USD per dt) | $ / decatherm	12.09	11.33
Level 3 | Forward Contract | Weighted Average
Liabilities
Forward price (in USD per dt) | $ / decatherm	3.01	2.71
Measurement at fair value on recurring basis
Assets
Available-for-Sale Securities	$ 36	$ 32
Derivatives - Energy Related Assets	48,127	80,893
Assets	48,163	80,925
Liabilities
Derivatives - Energy Related Liabilities	52,963	64,622
Derivatives - Other	10,370	10,030
Liabilities	63,333	74,652
Measurement at fair value on recurring basis | Level 1
Assets
Available-for-Sale Securities	36	32
Derivatives - Energy Related Assets	5,155	33,994
Assets	5,191	34,026
Liabilities
Derivatives - Energy Related Liabilities	10,687	16,502
Derivatives - Other	0	0
Liabilities	10,687	16,502
Measurement at fair value on recurring basis | Level 2
Assets
Available-for-Sale Securities	0	0
Derivatives - Energy Related Assets	21,869	11,814
Assets	21,869	11,814
Liabilities
Derivatives - Energy Related Liabilities	24,283	22,070
Derivatives - Other	10,370	10,030
Liabilities	34,653	32,100
Measurement at fair value on recurring basis | Level 3
Assets
Available-for-Sale Securities	0	0
Derivatives - Energy Related Assets	21,103	35,085
Assets	21,103	35,085
Liabilities
Derivatives - Energy Related Liabilities	17,993	26,050
Derivatives - Other	0	0
Liabilities	17,993	26,050
South Jersey Gas Company
Changes in significant unobservable inputs [Roll forward]
Balance at beginning of period	926	183
Other changes in fair value from continuing and new contracts, net	2,258	926
Transfers in to/(out of) of Level 3		(206)
Settlements	(926)	(183)
Balance at end of period	$ 2,052	$ 926
South Jersey Gas Company | Level 3 | Forward Contract | Minimum
Liabilities
Forward price (in USD per dt) | $ / decatherm	2.42	3.25
South Jersey Gas Company | Level 3 | Forward Contract | Maximum
Liabilities
Forward price (in USD per dt) | $ / decatherm	6.67	6.33
South Jersey Gas Company | Level 3 | Forward Contract | Weighted Average
Liabilities
Forward price (in USD per dt) | $ / decatherm	5.25	5.09
South Jersey Gas Company | Measurement at fair value on recurring basis
Assets
Derivatives - Energy Related Assets	$ 7,332	$ 5,807
Assets	7,332	5,807
Liabilities
Derivatives - Energy Related Liabilities	9,440	1,372
Derivatives - Other	7,028	7,365
Liabilities	16,468	8,737
South Jersey Gas Company | Measurement at fair value on recurring basis | Level 1
Assets
Derivatives - Energy Related Assets	208	4,767
Assets	208	4,767
Liabilities
Derivatives - Energy Related Liabilities	1,750	6
Derivatives - Other	0	0
Liabilities	1,750	6
South Jersey Gas Company | Measurement at fair value on recurring basis | Level 2
Assets
Derivatives - Energy Related Assets	230	0
Assets	230	0
Liabilities
Derivatives - Energy Related Liabilities	2,848	1,252
Derivatives - Other	7,028	7,365
Liabilities	9,876	8,617
South Jersey Gas Company | Measurement at fair value on recurring basis | Level 3
Assets
Derivatives - Energy Related Assets	6,894	1,040
Assets	6,894	1,040
Liabilities
Derivatives - Energy Related Liabilities	4,842	114
Derivatives - Other	0	0
Liabilities	4,842	114
Natural Gas (in MMdts) | Level 3 | Forward Contract
Liabilities
Assets	13,519	23,301
Liabilities	15,686	18,109
Natural Gas (in MMdts) | South Jersey Gas Company | Level 3 | Forward Contract
Liabilities
Assets	6,894	1,040
Liabilities	4,842	114
Electricity (in MMmwh) | Level 3 | Forward Contract
Liabilities
Assets	7,584	11,784
Liabilities	$ 2,307	$ 7,941
Electricity (in MMmwh) | Level 3 | Forward Contract | Minimum | On-peak
Liabilities
Fixed electric load profile	36.36%	21.43%
Electricity (in MMmwh) | Level 3 | Forward Contract | Minimum | Off-peak
Liabilities
Fixed electric load profile	0.00%	0.00%
Electricity (in MMmwh) | Level 3 | Forward Contract | Maximum | On-peak
Liabilities
Fixed electric load profile	100.00%	100.00%
Electricity (in MMmwh) | Level 3 | Forward Contract | Maximum | Off-peak
Liabilities
Fixed electric load profile	63.64%	78.57%
Electricity (in MMmwh) | Level 3 | Forward Contract | Weighted Average | On-peak
Liabilities
Fixed electric load profile	53.39%	55.14%
Electricity (in MMmwh) | Level 3 | Forward Contract | Weighted Average | Off-peak
Liabilities
Fixed electric load profile	46.61%	44.86%