SIGNIFICANT ACCOUNTING POLICIES - Ownership Interests Acquired (Details)	Jun. 01, 2017
PNGTS
Acquisitions
Interest acquired (as a percent)	11.81%
Ownership interest (as a percent)	11.81%
Iroquois
Acquisitions
Interest acquired (as a percent)	49.34%
PNGTS
Acquisitions
Ownership interest, including acquired interest (as a percent)	61.71%

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Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
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-Section 50
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Percentage of voting equity interests acquired in a business combination achieved in stages, including equity interests in the acquiree held by the acquirer immediately before the acquisition date and acquired at the acquisition date.

+ References

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
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-Paragraph 3
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