Net Income Per Common Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic Net Income per Common Unit
Net income attributable to PAA	$ 449	$ 710	$ 1,865	$ 1,099
Distributions to participating securities	(1)	(1)	(2)	(2)
Other		(2)	(4)	(2)
Net income allocated to common unitholders	399	658	1,710	946
Diluted Net Income per Common Unit
Net income attributable to PAA	449	710	1,865	1,099
Distributions to participating securities	(1)	(1)	(2)	(2)
Other				(1)
Net income allocated to common unitholders	436	697	1,826	947
Series A Preferred Units
Basic Net Income per Common Unit
Distributions to preferred unitholders	(37)	(37)	(112)	(112)
Diluted Net Income per Common Unit
Distributions to preferred unitholders				(112)
Series B Preferred Units
Basic Net Income per Common Unit
Distributions to preferred unitholders	(12)	(12)	(37)	(37)
Diluted Net Income per Common Unit
Distributions to preferred unitholders	$ (12)	$ (12)	$ (37)	$ (37)
Common Units
Basic Net Income per Common Unit
Basic weighted average common units outstanding (units)	728	726	727	726
Basic net income per common unit (usd per unit)	$ 0.55	$ 0.91	$ 2.35	$ 1.30
Diluted Net Income per Common Unit
Basic weighted average common units outstanding (units)	728	726	727	726
Effect of dilutive securities:
Series A preferred units (units)	71	71	71
Equity-indexed compensation plan awards (units)	1	2	2	2
Diluted weighted average common units outstanding (units)	800	799	800	728
Diluted net income per common unit (usd per unit)	$ 0.55	$ 0.87	$ 2.28	$ 1.30