Net Income/(Loss) Per Common Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic Net Income/(Loss) per Common Unit
Net income/(loss) attributable to PAA	$ (28)	$ 143	$ 142	$ (2,847)	$ 306	$ 449	$ 446	$ 970	$ (2,590)	$ 2,171	$ 2,216
Distributions to participating securities									(2)	(3)	(3)
Other									0	(3)	(6)
Net income/(loss) allocated to common unitholders									(2,790)	1,967	2,009
Diluted Net Income/(Loss) per Common Unit
Net income/(loss) attributable to PAA	$ (28)	$ 143	$ 142	$ (2,847)	$ 306	$ 449	$ 446	$ 970	(2,590)	2,171	2,216
Distributions to participating securities									(2)	(3)	(3)
Other									0	0	0
Net income/(loss) allocated to common unitholders									$ (2,790)	2,119	2,164
Equity-indexed Compensation Plan Award | Weighted Average
Net Income Per Common Unit
Antidilutive securities excluded from computation of earnings per unit (in units)									0.3
Series B Preferred Units
Basic Net Income/(Loss) per Common Unit
Distributions to preferred unitholders									$ (49)	(49)	(49)
Diluted Net Income/(Loss) per Common Unit
Distributions to preferred unitholders									$ (49)	$ (49)	$ (49)
Common Units
Basic Net Income/(Loss) per Common Unit
Basic weighted average common units outstanding (in units)									728.0	727.0	726.0
Basic net income/(loss) per common unit (in dollars per unit)	$ (0.11)	$ 0.13	$ 0.13	$ (3.98)	$ 0.35	$ 0.55	$ 0.54	$ 1.26	$ (3.83)	$ 2.70	$ 2.77
Diluted Net Income/(Loss) per Common Unit
Basic weighted average common units outstanding (in units)									728.0	727.0	726.0
Effect of dilutive securities:
Series A preferred units (in units)									0.0	71.0	71.0
Equity-indexed compensation plan awards (in units)									0.0	2.0	2.0
Diluted weighted average common units outstanding (in units)									728.0	800.0	799.0
Diluted net income/(loss) per common unit (in dollars per unit)	$ (0.11)	$ 0.13	$ 0.13	$ (3.98)	$ 0.35	$ 0.55	$ 0.54	$ 1.20	$ (3.83)	$ 2.65	$ 2.71
Series A Preferred Units
Basic Net Income/(Loss) per Common Unit
Distributions to preferred unitholders									$ (149)	$ (149)	$ (149)
Diluted Net Income/(Loss) per Common Unit
Distributions to preferred unitholders									$ (149)	$ 0	$ 0
Series A Preferred Units | Weighted Average
Net Income Per Common Unit
Antidilutive securities excluded from computation of earnings per unit (in units)									71.0