CHANGE IN OPERATING WORKING CAPITAL - Components (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CHANGE IN OPERATING WORKING CAPITAL
Change in accounts receivable and other	$ 11	$ 2
Change in other current assets	2	2
Change in accounts payable and accrued liabilities	(5)	1
Change in accounts payable to affiliates	(2)	(2)
Change in state income taxes payable		8
Change in accrued interest	1	1
Change in operating working capital	$ 7	$ 12	[1]

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