Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

+ Details

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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- Details

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- Details

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SIGNIFICANT ACCOUNTING POLICIES - Basis of Presentation (Details)	Sep. 30, 2017	Aug. 01, 2017	Jun. 01, 2017	Sep. 30, 2016
Portland Natural Gas Transmission System
ACQUISITION
Ownership interest (as a percent)	11.81%		11.81%	49.90%
Iroquois
ACQUISITION
Ownership interest (as a percent)	49.34%	49.34%	49.34%
Portland Natural Gas Transmission System
ACQUISITION
Ownership interest (as a percent)			11.81%
Interest acquired by Partnership (as a percent)			61.71%