PARTNERS' EQUITY - Reclassification of units (Details) - USD ($) shares in Millions, $ in Millions		2 Months Ended	4 Months Ended	9 Months Ended
		May 19, 2016	Sep. 30, 2017	Sep. 30, 2017		Dec. 31, 2016
PARTNERS' EQUITY
Common units subject to rescission	[1]					$ 83
Reclassification of common units no longer subject to rescission			$ 83	$ 83	[2]
ATM Equity Issuance Program | Common Units
PARTNERS' EQUITY
Reclassification of common unit issuance subject to rescission, net (in units)		1.6
Common units subject to rescission			$ 0	$ 0		$ 83

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

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