ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Changes in accumulated other comprehensive income (loss) (AOCI) by component
Partners' Equity at beginning of year	[1],[2]	$ 1,144
Change in fair value of cash flow hedges		5	$ 3	[2]
PNGTS' Amortization of realized loss on derivative financial instrument (Note 19)		1	1	[2]	$ 1	[2]
Net other comprehensive income	[3]	7	3		1
Partners' Equity at end of year		963	1,144	[1],[2]
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss) (AOCI) by component
Partners' Equity at beginning of year		(2)	(4)		(5)
Change in fair value of cash flow hedges		5	3
Amounts reclassified from AOCI			(2)
PNGTS' Amortization of realized loss on derivative financial instrument (Note 19)		1	1		1
Other comprehensive income - effects of Iroquois' retirement benefit plans		1
Net other comprehensive income		7	2		1
Partners' Equity at end of year		5	(2)		(4)
Cash flow hedges
Changes in accumulated other comprehensive income (loss) (AOCI) by component
Partners' Equity at beginning of year		(2)	(4)		(5)
Change in fair value of cash flow hedges		5	3
Amounts reclassified from AOCI			(2)
PNGTS' Amortization of realized loss on derivative financial instrument (Note 19)		1	1		1
Net other comprehensive income		6	2		1
Partners' Equity at end of year		4	$ (2)		$ (4)
Equity Investments
Changes in accumulated other comprehensive income (loss) (AOCI) by component
Other comprehensive income - effects of Iroquois' retirement benefit plans		1
Net other comprehensive income		1
Partners' Equity at end of year		$ 1

[1] Recast to consolidate PNGTS (Refer to Notes 2 and 7).

[2] Recast to consolidate PNGTS (Refer to Notes 2 and 7).

[3] Recast to consolidate PNGTS (Refer to Notes 2 and 7).