ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassifications out of AOCL (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income Taxes	$ 24,949	$ 36,415
Net Income	85,637	$ 111,240
Amounts reclassified from AOCL	$ (8)
Combined statutory tax rate	27.00%	25.00%
SJG Utility Operations
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income Taxes	$ 23,697	$ 21,836
Net Income	68,731	$ 66,747
Amounts reclassified from AOCL	$ (8)
Combined statutory tax rate	27.00%	25.00%
Unrealized Gain (Loss) on Derivatives-Other
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCL	$ (8)
Unrealized Gain (Loss) on Derivatives-Other \| SJG Utility Operations
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCL	(8)
Reclassification out of Accumulated Other Comprehensive Income \| Accumulated Net Investment Gain (Loss) Attributable to Noncontrolling Interest
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income Taxes	(4)
Reclassification out of Accumulated Other Comprehensive Income \| Unrealized Gain (Loss) on Derivatives-Other \| SJG Utility Operations
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income Taxes	(4)
Net Income	8
Interest Charges \| Reclassification out of Accumulated Other Comprehensive Income \| Accumulated Net Investment Gain (Loss) Attributable to Noncontrolling Interest
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Unrealized Loss on Derivatives-Other - interest rate contracts designated as cash flow hedges	12
Interest Charges \| Reclassification out of Accumulated Other Comprehensive Income \| Unrealized Gain (Loss) on Derivatives-Other \| SJG Utility Operations
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Unrealized Loss on Derivatives-Other - interest rate contracts designated as cash flow hedges	$ 12

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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