Net Income Per Common Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended								12 Months Ended			22 Months Ended
	Nov. 15, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 14, 2016
Net Income Per Common Unit
General partner ownership interest													2.00%
Basic Net Income per Common Unit
Net income attributable to PAA		$ 1,117	$ 710	$ 100	$ 288	$ 191	$ 33	$ 188	$ 444	$ 2,216	$ 856	$ 726
Distributions to general partner												(412)
Distributions to participating securities										(3)	(2)	(4)
Undistributed loss allocated to general partner												14
Other										(6)	(16)	(2)
Net income allocated to common unitholders										2,009	685	200
Diluted Net Income per Common Unit
Net income attributable to PAA		$ 1,117	$ 710	$ 100	$ 288	$ 191	$ 33	$ 188	$ 444	2,216	856	726
Distributions to general partner												(412)
Distributions to participating securities										(3)	(2)	(4)
Undistributed loss allocated to general partner												14
Other											(16)	(2)
Net income allocated to common unitholders										2,164	685	200
Series A Preferred Units
Basic Net Income per Common Unit
Distributions to preferred unitholders										(149)	(142)	(122)
Diluted Net Income per Common Unit
Distributions to preferred unitholders											(142)	$ (122)
Series B Preferred Units
Basic Net Income per Common Unit
Distributions to preferred unitholders										(49)	(11)
Diluted Net Income per Common Unit
Distributions to preferred unitholders										$ (49)	$ (11)
Common Units
Net Income Per Common Unit
Weighted Average Number Diluted Limited Partnership Units Outstanding Adjustment, Series A Preferred Units										71		0
Basic Net Income per Common Unit
Basic weighted average common units outstanding (in units)										726	717	464
Basic net income per common unit (in dollars per unit)		$ 1.46	$ 0.91	$ 0.07	$ 0.33	$ 0.19	$ (0.01)	$ 0.21	$ 0.59	$ 2.77	$ 0.96	$ 0.43
Diluted Net Income per Common Unit
Basic weighted average common units outstanding (in units)										726	717	464
Effect of dilutive securities:
Equity-indexed compensation plan awards (in units)										2	1	2
Diluted weighted average common units outstanding (in units)										799	718	466
Diluted net income per common unit (in dollars per unit)		$ 1.38	$ 0.87	$ 0.07	$ 0.33	$ 0.19	$ (0.01)	$ 0.21	$ 0.58	$ 2.71	$ 0.95	$ 0.43
Simplification Transactions | PAA GP
Net Income Per Common Unit
Economic ownership interest converted into non-economic interest	2.00%