REGULATORY ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	$ 38,372	$ 54,420
Regulatory Assets, Noncurrent	424,304	437,479
Regulatory Liability, Current	(46,534)	(48,394)
Regulatory Liability, Noncurrent	(508,877)	(520,866)
Net regulatory assets (liabilities), current	(8,162)	6,026
Net regulatory assets (liabilities), noncurrent	(84,573)	(83,387)
Net Regulatory Assets	(92,735)	(77,361)
Federal income tax rate changes [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current	(15,755)	(30,934)
Regulatory Liability, Noncurrent	(508,877)	(520,866)
Regulatory Liabilities	(524,632)	(551,800)
Over-recovered purchased-gas costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current	(22,616)	(13,668)
Regulatory Liability, Noncurrent	0	0
Regulatory Liabilities	(22,616)	(13,668)
Total regulated liabilities [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current	(46,534)	(48,394)
Regulatory Liability, Noncurrent	(508,877)	(520,866)
Regulatory Liabilities	(555,411)	(569,260)
Under-recovered purchased-gas costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	767	25,083
Regulatory Assets, Noncurrent	0	0
Regulatory Assets	767	25,083
Pension and postretirement benefit costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	22,966	23,384
Regulatory Assets, Noncurrent	406,441	421,726
Regulatory Assets	429,407	445,110
Weather normalization [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current	(8,163)	(3,792)
Regulatory Liability, Noncurrent	0	0
Regulatory Liabilities	(8,163)	(3,792)
Reacquired debt costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	812	812
Regulatory Assets, Noncurrent	6,082	6,487
Regulatory Assets	6,894	7,299
Ad valorem tax [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	2,083	1,070
Regulatory Assets, Noncurrent	0	0
Regulatory Assets	2,083	1,070
MGP Costs [Member] [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	98	0
Regulatory Assets, Noncurrent	9,758	7,724
Regulatory Assets	9,856	7,724
Other regulatory assets [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	11,646	4,071
Regulatory Assets, Noncurrent	2,023	1,542
Regulatory Assets	13,669	5,613
Total regulatory assets, net of amortization [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	38,372	54,420
Regulatory Assets, Noncurrent	424,304	437,479
Regulatory Assets	$ 462,676	$ 491,899

The net amount of all current regulatory assets less all current regulatory liabilities as of the end of the period.

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The net amount of noncurrent regulatory assets less all noncurrent regulatory liabilities as of the end of the period.

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[Line Items] for Tabular disclosure of assets and liabilities that result from rate actions of a regulator. Regulatory assets are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability.

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The net amount of all regulatory assets less all regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

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The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 405
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

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The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.

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The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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