CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income/(loss)	$ 139	$ 431	$ (2,417)	$ 1,771
Other comprehensive income/(loss)	82	(99)	(129)	10
Comprehensive income/(loss)	221	332	(2,546)	1,781
Comprehensive (income)/loss attributable to noncontrolling interests	(183)	(285)	1,966	(1,496)
Comprehensive income/(loss) attributable to PAGP	$ 38	$ 47	$ (580)	$ 285