Net Income/(Loss) Per Common Unit (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 Common Unit
Net income/(loss) attributable to PAA	$ 593	$ (2,590)	$ 2,171
Distributions to participating securities	(2)	(2)	(3)
Other	0	0	(3)
Net income/(loss) allocated to common unitholders	393	(2,790)	1,967
Diluted Net Income/(Loss) per Common Unit
Net income/(loss) attributable to PAA	593	(2,590)	2,171
Distributions to participating securities	(2)	(2)	(3)
Net income/(loss) allocated to common unitholders	$ 393	$ (2,790)	2,119
Equity-indexed Compensation Plan Award | Weighted Average
Net Income Per Common Unit
Antidilutive securities excluded from computation of earnings per unit (in units)	0.5	0.3
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)	$ (149)	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	71.0
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)	716.0	728.0	727.0
Basic net income/(loss) per common unit (in dollars per unit)	$ 0.55	$ (3.83)	$ 2.70
Diluted Net Income/(Loss) per Common Unit
Basic weighted average common units outstanding (in units)	716.0	728.0	727.0
Effect of dilutive securities:
Series A preferred units (in units)	0.0	0.0	71.0
Equity-indexed compensation plan awards (in units)	0.0	0.0	2.0
Diluted weighted average common units outstanding (in units)	716.0	728.0	800.0
Diluted net income/(loss) per common unit (in dollars per unit)	$ 0.55	$ (3.83)	$ 2.65