SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Thousands, number in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Significant Accounting Policies [Line Items]
Impact of reclassification upon adoption of ASU 2017-07	$ 8,800	$ 17,300	$ 19,800
Operating Lease, Right-of-Use Asset	32,000
Operating Lease, Liability	$ 32,000
Number of natural gas distribution services customers	2
Allowance for Doubtful Accounts Receivable, Current	$ 4,700	4,800
Goodwill, Impairment Loss	0	0	0
Asset Impairment Charges	0	0	$ 0
Deferred Tax Assets, Valuation Allowance	0	0
Liability for Uncertainty in Income Taxes, Current	$ 0	$ 0
Segment Reporting, Disclosure of Major Customers	0	0	0