SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Significant Accounting Policies [Line Items]
Unbilled Receivables, Current	$ 141,700,000us-gaap_UnbilledReceivablesCurrent	$ 143,700,000us-gaap_UnbilledReceivablesCurrent
Number of natural gas distribution services customers	2,000,000
Allowance for Doubtful Accounts Receivable, Current	4,000,000	3,300,000
Materials, Supplies, and Other	27,500,000us-gaap_MaterialsSuppliesAndOther	16,600,000us-gaap_MaterialsSuppliesAndOther
Goodwill	157,953,000us-gaap_Goodwill	157,953,000us-gaap_Goodwill
Goodwill, Impairment Loss	0us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss
Asset Impairment Charges	0us-gaap_AssetImpairmentCharges	0us-gaap_AssetImpairmentCharges	0us-gaap_AssetImpairmentCharges
Deferred Tax Assets, Valuation Allowance	0	0
Liability for Uncertain Tax Positions, Current	$ 0	$ 0
Segment Reporting, Disclosure of Major Customers	0	0	0

Number of customers the natural gas distribution service segment services.

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- Definition

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Article 5

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-Name Accounting Standards Codification

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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-Publisher FASB

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-Topic 740

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The current portion of the amount recognized for uncertain tax positions as of the balance sheet date.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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The carrying amount of capitalized costs of materials, supplies, and other assets, which are not included in inventory but used in production.

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Disclosure of the extent of enterprise reliance on its major customers. For example, includes revenues from transactions with a single external customer amounting to 10 percent or more of the entity's revenues, the total amount of revenues from each such customer, and the identity of the segment or segments reporting the revenues. A group of entities that the entity knows to be under common control generally will be considered a single customer for inclusion in this item. The federal government, a state government, a local government (for example, a county or municipality), or a foreign government each will generally be considered as a single customer for inclusion in this item.

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Amount received for services rendered and products shipped, but not yet billed, for non-contractual agreements due within one year or the normal operating cycle, if longer.

+ References

No definition available.

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