ACCOUNTING PRONOUNCEMENTS - Statement of Cash Flows (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
ACCOUNTING PRONOUNCEMENTS
Distributions from equity investments	$ 68	$ 95	[1]
Adjustment | ASU 2016-15, Statement of Cash Flows
ACCOUNTING PRONOUNCEMENTS
Cumulative distributions in excess of equity earnings		(42)
Distributions from equity investments		$ 42

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