ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in accumulated other comprehensive income (loss) (AOCI) by component
Partners' Equity at beginning of year	$ 591
Change in fair value of interest rate derivative instruments recognized in other comprehensive income	(13)	$ (2)	$ 5
PNGTS' amortization of realized loss on derivative instrument (Note 20)		1	1
Net other comprehensive income	(13)	3	7
Partners' Equity at end of year	656	591
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss) (AOCI) by component
Partners' Equity at beginning of year	8	5	(2)
Change in fair value of interest rate derivative instruments recognized in other comprehensive income	(13)	(2)	5
Amounts reclassified from AOCI	(1)	5
PNGTS' amortization of realized loss on derivative instrument (Note 20)	1	1	1
Other comprehensive income (loss) - effects of Iroquois' retirement benefit plans		(1)	1
Net other comprehensive income	(13)	3	7
Partners' Equity at end of year	(5)	8	5
Cash flow hedges
Changes in accumulated other comprehensive income (loss) (AOCI) by component
Partners' Equity at beginning of year	8	4	(2)
Change in fair value of interest rate derivative instruments recognized in other comprehensive income	(13)	(2)	5
Amounts reclassified from AOCI	(1)	5
PNGTS' amortization of realized loss on derivative instrument (Note 20)		1	1
Net other comprehensive income	(14)	4	6
Partners' Equity at end of year	(6)	8	4
Equity Investments
Changes in accumulated other comprehensive income (loss) (AOCI) by component
Partners' Equity at beginning of year		1
PNGTS' amortization of realized loss on derivative instrument (Note 20)	1
Other comprehensive income (loss) - effects of Iroquois' retirement benefit plans		(1)	1
Net other comprehensive income	1	$ (1)	1
Partners' Equity at end of year	$ 1		$ 1

The amount of amortization of release loss on derivative instruments, net of tax.

No definition available.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount, after tax and before reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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- Definition

The amount of ownership interest of different classes of partners in limited partnership.

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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