Net Income/(Loss) Per Class A Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Basic Net Income/(Loss) per Class A Share
Net income/(loss) attributable to PAGP	$ 60	$ (568)	$ 331
Diluted Net Income/(Loss) per Class A Share
Net income/(loss) attributable to PAGP	60	(568)	331
Incremental net income/(loss) attributable to PAGP resulting from assumed exchange of AAP units and AAP Management Units	0	(189)	2
Net income/(loss) attributable to PAGP including incremental net income/(loss) from assumed exchange of AAP units and AAP Management Units	$ 60	$ (757)	$ 333
AAP Units
Basic and diluted earnings per share
Antidilutive securities excluded from computation of earnings per share (in shares)	50.0		99.0
AAP Management Units
Basic and diluted earnings per share
Antidilutive securities excluded from computation of earnings per share (in shares)	1.0	1.0
Class A Shares
Basic Net Income/(Loss) per Class A Share
Basic weighted average Class A shares outstanding (in shares)	194.0	186.0	168.0
Basic net income/(loss) per Class A share (in dollars per share)	$ 0.31	$ (3.06)	$ 1.97
Diluted Net Income/(Loss) per Class A Share
Basic weighted average Class A shares outstanding (in shares)	194.0	186.0	168.0
Dilutive shares resulting from assumed exchange of AAP units and AAP Management Units (in shares)	0.0	60.0	2.0
Diluted weighted average Class A shares outstanding (in shares)	194.0	246.0	170.0
Diluted net income/(loss) per Class A share (in dollars per share)	$ 0.31	$ (3.07)	$ 1.96
Maximum
Basic and diluted earnings per share
Dilutive award (in shares)	0.1		0.1