BUSINESS COMBINATIONS (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended
	Jul. 01, 2018	Oct. 31, 2018	Mar. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Payments to acquire businesses	$ 1,740,000
Working capital adjustment	40,300
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Property, Plant and Equipment	1,089,342
Accounts Receivable	45,875
Provision for Uncollectibles	(6,579)
Natural Gas in Storage	12,204
Materials and Supplies	345
Other Prepayments and Current Assets	200
Deferred Income Taxes	21,024
Regulatory Assets	136,213
Goodwill	731,029		$ 734,607	$ 734,600
Total assets acquired	2,029,653
Accounts Payable	13,089
Other Current Liabilities	9,185
Environmental Remediation Costs - Current	7,100
Pension and Other Postretirement Benefits	3,213
Environmental Remediation Costs - Non Current	66,165
Regulatory Liabilities	189,509
Other	1,107
Total liabilities assumed	289,368
Total net assets acquired	1,740,285
Goodwill deductible for tax purposes	731,000		677,600
ETG and ELK revenues included in the Company's unaudited consolidated statements of income			143,500
ETG and ELK earnings included in the Company's unaudited consolidated statements of income			$ 31,300
Elizabethtown Gas
Business Acquisition [Line Items]
Payments to acquire businesses	1,730,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Credits due to customers under conditions of approval	15,000
Elkton Gas
Business Acquisition [Line Items]
Payments to acquire businesses	10,900
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Credits due to customers under conditions of approval	$ 300
Elizabethtown Gas | New Jersey Board of Public Utilities
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Requested amount to be recovered		$ 518,000