PLANT, PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
PLANT, PROPERTY AND EQUIPMENT
Cost	$ 3,304	$ 3,268
Accumulated Depreciation	(1,181)	(1,088)
Net Book Value	2,123	2,180	[1]
Pipeline
PLANT, PROPERTY AND EQUIPMENT
Cost	2,577	2,540
Accumulated Depreciation	(962)	(879)
Net Book Value	1,615	1,661
Compression
PLANT, PROPERTY AND EQUIPMENT
Cost	533	519
Accumulated Depreciation	(165)	(148)
Net Book Value	368	371
Metering and other equipment
PLANT, PROPERTY AND EQUIPMENT
Cost	182	205
Accumulated Depreciation	(54)	(61)
Net Book Value	128	144
Construction in progress
PLANT, PROPERTY AND EQUIPMENT
Cost	12	4
Net Book Value	$ 12	$ 4

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