FINANCIAL CHARGES AND OTHER (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
FINANCIAL CHARGES AND OTHER
Interest Expense	$ 83	$ 69		$ 65
Net realized loss related to the interest rate swaps		3		2
PNGTS' amortization of realized loss on derivative instrument (Note 19)	1	1		1
Other	(2)	(2)		(5)
Financial charges and other	$ 82	$ 71	[1]	$ 63	[1]

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