CONSOLIDATED STATEMENT OF CHANGES IN PARTNERS' EQUITY - USD ($) shares in Millions, $ in Millions	ATM Equity Issuance Program Limited Partners Common Units	ATM Equity Issuance Program General Partner	ATM Equity Issuance Program	Limited Partners PNGTS Common Units	Limited Partners Common Units	Limited Partners Class B Units	General Partner PNGTS	General Partner	Accumulated Other Comprehensive Income (Loss)	PNGTS Equity of former parent of PNGTS	PNGTS	Non-Controlling Interest	Equity of former parent of PNGTS	Total
Partners' Equity at beginning of period at Dec. 31, 2016					$ 1,002	$ 117		$ 27	$ (2)			$ 97	$ 31	$ 1,272
Partners' Equity at beginning of period (in units) at Dec. 31, 2016					67.4	1.9
Increase (Decrease) in Partners' Equity
Net income (loss)					$ 219	$ 15		16				11	2	263
Other comprehensive income (loss)									7					7
ATM equity issuances, net (Note 11)	$ 173	$ 3	$ 176
ATM equity issuances, net (Note 11) (in units)	3.2
Reclassification of common unit issuance subject to rescission, net (Note 11)					81			2						83
Acquisition of interests (note 8)				$ (383)			$ (8)			$ (32)	$ (423)
Distributions (Note 10)					(268)	(22)		(16)				(3)	$ (1)	(310)
Partners' Equity at end of period at Dec. 31, 2017					$ 824	$ 110		24	5			105		1,068
Partners' Equity at end of period (in units) at Dec. 31, 2017					70.6	1.9
Increase (Decrease) in Partners' Equity
Net income (loss)					$ (191)	$ 13		(4)				17		(165)
Other comprehensive income (loss)									3					3
ATM equity issuances, net (Note 11)	$ 39	$ 1	$ 40
ATM equity issuances, net (Note 11) (in units)	0.7
Distributions (Note 10)					(210)	(15)		(8)				(14)		(247)
Partners' Equity at end of period at Dec. 31, 2018					$ 462	$ 108		13	8			108		699
Partners' Equity at end of period (in units) at Dec. 31, 2018					71.3	1.9
Increase (Decrease) in Partners' Equity
Net income (loss)					$ 267	$ 8		5				18		298
Other comprehensive income (loss)									(13)					(13)
Distributions (Note 10)					(185)	(13)		(4)				(22)		(224)
Partners' Equity at end of period at Dec. 31, 2019					$ 544	$ 103		$ 14	$ (5)			$ 104		$ 760
Partners' Equity at end of period (in units) at Dec. 31, 2019					71.3	1.9