CHANGE IN OPERATING WORKING CAPITAL - Components (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CHANGE IN OPERATING WORKING CAPITAL
Change in accounts receivable and other	$ 13	$ 3
Change in other current assets	1	2
Change in accounts payable and accrued liabilities	2	3
Change in accounts payable to affiliates	(3)	(2)
Change in accrued interest	11	5
Change in operating working capital	$ 24	$ 11	[1]

[1] Recast to consolidate PNGTS for all periods presented (Refer to Notes 2 and 6).