Net Income Per Class A Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic Net Income per Class A Share
Net income attributable to PAGP	$ (8)	$ 24	$ 42	$ 36	$ 25	$ 32	$ 30	$ 31	$ 94	$ 118	$ 70
Diluted Net Income per Class A Share
Net income attributable to PAGP	$ (8)	$ 24	$ 42	$ 36	$ 25	$ 32	$ 30	$ 31	94	118	70
Incremental net income attributable to PAGP resulting from assumed exchange of AAP units and AAP Management Units									0	0	235
Net income attributable to PAGP including incremental net income from assumed exchange of AAP units and AAP Management Units									$ 94	$ 118	$ 305
Maximum
Basic and diluted earnings per share
Dilutive awards (less than 0.1 million) (in shares)									0.1	0.1	0.1
Class A Shares
Basic Net Income per Class A Share
Basic weighted average Class A shares outstanding (in shares)									99.0	83.0	54.0
BASIC NET INCOME PER CLASS A SHARE (in dollars per share)	$ (0.08)	$ 0.24	$ 0.43	$ 0.37	$ 0.29	$ 0.37	$ 0.37	$ 0.37	$ 0.94	$ 1.41	$ 1.28
Diluted Net Income per Class A Share
Basic weighted average Class A shares outstanding (in shares)									99.0	83.0	54.0
Dilutive shares resulting from assumed exchange of AAP units and AAP Management Units (in shares)									0.0	0.0	190.0
Diluted weighted average Class A shares outstanding (in shares)									99.0	83.0	244.0
DILUTED NET INCOME PER CLASS A SHARE (in dollars per share)	$ (0.08)	$ 0.24	$ 0.40	$ 0.37	$ 0.29	$ 0.37	$ 0.37	$ 0.37	$ 0.94	$ 1.41	$ 1.25