Net Income/(Loss) Per Common Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ 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 Common Unit
Net income/(loss) attributable to PAA	$ 142	$ 446	$ (2,705)	$ 1,416
Distributions to participating securities	(1)	(1)	(1)	(2)
Other		(1)		(4)
Net income/(loss) allocated to common unitholders	92	395	(2,805)	1,311
Diluted Net Income/(Loss) per Common Unit
Net income/(loss) attributable to PAA	142	446	(2,705)	1,416
Distributions to participating securities	(1)	(1)	(1)	(2)
Net income/(loss) allocated to common unitholders	$ 92	433	$ (2,805)	1,389
Weighted average
Net Income/(Loss) Per Common Unit
Dilutive LTIP awards (units)	0.1
Weighted average | LTIP awards
Net Income/(Loss) Per Common Unit
Antidilutive securities excluded from computation of earnings per unit (units)			0.5
Series A Preferred Units
Basic Net Income/(Loss) per Common Unit
Distributions to preferred unitholders	$ (37)	(37)	$ (74)	(74)
Diluted Net Income/(Loss) per Common Unit
Distributions to preferred unitholders	$ (37)		$ (74)
Series A Preferred Units | Weighted average
Net Income/(Loss) Per Common Unit
Antidilutive securities excluded from computation of earnings per unit (units)	71.0		71.0
Series B Preferred Units
Basic Net Income/(Loss) per Common Unit
Distributions to preferred unitholders	$ (12)	(12)	$ (25)	(25)
Diluted Net Income/(Loss) per Common Unit
Distributions to preferred unitholders	$ (12)	$ (12)	$ (25)	$ (25)
Common Units
Basic Net Income/(Loss) per Common Unit
Basic weighted average common units outstanding (units)	728.0	727.0	728.0	727.0
Basic net income/(loss) per common unit (usd per unit)	$ 0.13	$ 0.54	$ (3.85)	$ 1.80
Diluted Net Income/(Loss) per Common Unit
Basic weighted average common units outstanding (units)	728.0	727.0	728.0	727.0
Effect of dilutive securities:
Series A preferred units (units)		71.0		71.0
Equity-indexed compensation plan awards (units)		2.0		2.0
Diluted weighted average common units outstanding (units)	728.0	800.0	728.0	800.0
Diluted net income/(loss) per common unit (usd per unit)	$ 0.13	$ 0.54	$ (3.85)	$ 1.74