Net Income Per Class A Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Basic Net Income per Class A Share
Net income attributable to PAGP from continuing operations	$ 62	$ 1	$ 119	$ 70
Net income attributable to PAGP from discontinued operations	21	32	79	44
Diluted Net Income per Class A Share
Incremental net income attributable to PAGP resulting from assumed exchange of AAP Management Units	3	0	11	0
Net income attributable to PAGP from discontinued operations including incremental net income from assumed exchange of AAP Management Units	$ 24	$ 32	$ 90	$ 44
Class A Shares
Basic Net Income per Class A Share
Basic weighted average Class A shares outstanding (in shares)	198,000	197,000	198,000	197,000
Basic Net Income per Class A Share:
Continuing operations (in usd per share)	$ 0.31	$ 0.01	$ 0.60	$ 0.36
Discontinued operations (in usd per share)	0.11	0.16	0.40	0.22
Basic net income per Class A share (in usd per share)	$ 0.42	$ 0.17	$ 1.00	$ 0.58
Diluted Net Income per Class A Share
Dilutive shares resulting from assumed exchange of AAP Management Units (in shares)	35,000	0	35,000
Diluted weighted average Class A shares outstanding (in shares)	233,000	197,000	233,000	197,000
Diluted Net Income per Class A Share:
Continuing operations (in usd per share)	$ 0.31	$ 0.01	$ 0.60	$ 0.36
Discontinued operations (in usd per share)	0.10	0.16	0.39	0.22
Diluted net income per Class A share (in usd per share)	$ 0.41	$ 0.17	$ 0.99	$ 0.58
Weighted Average | AAP Units | Held-for-Sale | NGL Business
Basic and Diluted Net Income Per Share
Antidilutive securities excluded from computation of earnings per share (shares)	35,000		35,000