Net Income/(Loss) Per Class A Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic Net Income/(Loss) per Class A Share
Net income/(loss) attributable to PAGP	$ 16	$ 66	$ (565)	$ 213
Diluted Net Income/(Loss) per Class A Share
Net income/(loss) attributable to PAGP	16	66	(565)	213
Incremental net income attributable to PAGP resulting from assumed exchange of AAP Management Units	0	0	0	0
Net income/(loss) attributable to PAGP including incremental net income from assumed exchange of AAP Management Units	$ 16	$ 66	$ (565)	$ 213
AAP Units
Net Income Per Class A Share
Antidilutive securities excluded from computation of earnings per share (per share)	63,000	112,000	64,000	116,000
AAP Management Units
Net Income Per Class A Share
Antidilutive securities excluded from computation of earnings per share (per share)	1,000		1,000	2,000
Class A Shares
Basic Net Income/(Loss) per Class A Share
Basic weighted average Class A shares outstanding (in shares)	184,000	162,000	183,000	161,000
Basic net income/(loss) per Class A share (in dollars per share)	$ 0.09	$ 0.41	$ (3.08)	$ 1.32
Diluted Net Income/(Loss) per Class A Share
Dilutive shares resulting from assumed exchange of AAP Management Units (in shares)		2,000
Diluted weighted average Class A shares outstanding (in shares)	184,000	164,000	183,000	161,000
Diluted net income/(loss) per Class A share (in dollars per share)	$ 0.09	$ 0.40	$ (3.08)	$ 1.32
Maximum
Net Income Per Class A Share
Dilutive LTIP awards (shares)		100		100