CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income/(loss)	$ (212)	$ 137	$ 181	$ (2,556)
Other comprehensive income/(loss)		116	108	(212)
Comprehensive income/(loss)	(212)	253	289	(2,768)
Comprehensive (income)/loss attributable to noncontrolling interests	143	(207)	(259)	2,150
Comprehensive income/(loss) attributable to PAGP	$ (69)	$ 46	$ 30	$ (618)