The percentage of distribution finance by borrowings.

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- Definition

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

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No definition available.

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Distributions received from equity investments relating to both operating and investing activities.

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This item represents the entity's proportionate share for the period of the undistributed earnings of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied.

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No definition available.

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Amount of equity impact of cash distribution declared to unit-holder of limited partnership (LP).

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Amount of cash distribution paid to unit-holder of limited partnership (LP).

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- Definition

Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

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Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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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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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

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Amount of distribution received from equity method investee for return of investment, classified as investing activities. Excludes distribution for return on investment, classified as operating activities.

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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.

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No definition available.

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EQUITY INVESTMENTS - Narrative (Details) - USD ($)			1 Months Ended			12 Months Ended
EQUITY INVESTMENTS - Narrative (Details) - USD ($)	Jan. 06, 2020	Nov. 01, 2019	Dec. 31, 2020	Aug. 31, 2019	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2006
Schedule of Equity Method Investments [Line Items]
Distributions received from equity investments						$ 225,000,000	$ 258,000,000	$ 198,000,000
Return on investment distribution classified as investing activities						29,000,000	58,000,000	10,000,000
Partnership's share of distributions						196,000,000	200,000,000	188,000,000
Distribution made to limited partner, cash distributions paid						8,000,000	13,000,000	15,000,000
Northern Border
Schedule of Equity Method Investments [Line Items]
Distributions received from equity investments						91,000,000	144,000,000	83,000,000
Return on investment distribution classified as investing activities						$ 0	50,000,000	0
Ownership interest			50.00%			50.00%
Undistributed earnings						$ 0	0	0
Difference between carrying amount and underlying equity			$ 115,000,000			115,000,000	$ 115,000,000
Additional ownership percentage									20.00%
Northern Border \| Northern Border
Schedule of Equity Method Investments [Line Items]
Ownership interest							50.00%
Great Lakes
Schedule of Equity Method Investments [Line Items]
Distributions received from equity investments						$ 48,000,000	$ 59,000,000	58,000,000
Ownership interest			46.45%			46.45%
Undistributed earnings						$ 0	0	0
Difference between carrying amount and underlying equity			$ 260,000,000			260,000,000	260,000,000
Equity contribution						10,000,000	10,000,000	9,000,000
Iroquois
Schedule of Equity Method Investments [Line Items]
Distributions received from equity investments						86,000,000	55,000,000	56,000,000
Return on investment distribution classified as investing activities						$ 29,000,000	8,000,000	10,000,000
Ownership interest	49.34%		49.34%			49.34%
Partnership's share of distributions	$ 14,000,000
Undistributed earnings						$ 0	0	0
Difference between carrying amount and underlying equity			$ 39,000,000			39,000,000	40,000,000
Equity contribution			$ 2,000,000	$ 4,000,000		2,000,000	4,000,000	$ 0
Northern Border
Schedule of Equity Method Investments [Line Items]
Distribution made to limited partner, cash distributions paid					$ 100,000,000
Distribution finance by borrowings, percent					100.00%
Northern Border \| Revolving Credit Facility
Schedule of Equity Method Investments [Line Items]
Maximum borrowing capacity					$ 200,000,000
Iroquois
Schedule of Equity Method Investments [Line Items]
Return on investment distribution classified as investing activities						$ 5,000,000	$ 8,000,000
Ownership interest			49.34%			49.34%
Partnership's share of distributions						$ 4,000,000
Limited partners, Distribution declared		$ 28,000,000
Iroquois \| Special distribution, terminated project guaranteed proceeds
Schedule of Equity Method Investments [Line Items]
Return on investment distribution classified as investing activities						$ 24,000,000