CHANGE IN OPERATING WORKING CAPITAL - Components (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CHANGE IN OPERATING WORKING CAPITAL
Change in accounts receivable and other	$ (6)	$ 4	$ (4)
Change in other current assets	(1)	2	(4)
Change in accounts payable and other current liabilities	3	(7)	5
Change in accounts payable to affiliates	1	(3)
Change in accrued interest		2	2
Change in operating working capital (Note 15)	$ (3)	$ (2)	$ (1)	[1]

[1] Recast to consolidate PNGTS (Refer to Notes 2 and 8).