Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ 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
Total revenues	$ 5,963	$ 5,833	$ 3,225	$ 8,269	$ 9,154	$ 7,886	$ 8,253	$ 8,375	$ 23,290	$ 33,669	$ 34,055
Gross margin	5	314	282	(189)	403	566	526	790	411	2,285
Operating income/(loss)	(65)	253	210	(2,773)	331	492	451	714	(2,375)	1,988	2,277
Net income/(loss)	(25)	146	144	(2,845)	307	454	448	970	(2,580)	2,180	2,216
Net income/(loss) attributable to PAA	(28)	143	142	(2,847)	$ 306	$ 449	$ 446	$ 970	(2,590)	2,171	2,216
Goodwill impairment losses				2,515					2,515	0	$ 0
Non-cash impairment losses upon classification to assets held for sale				167
Gain on/(impairment of) investments in unconsolidated entities, net
Write down of investments		91	$ 69	43
Gain on/(impairment of) investments in unconsolidated entities, net | Capline Pipeline Company LLC
Gain from remeasurement to fair value of retained investment		$ 2		267						$ 269
(Gains)/losses on asset sales and asset impairments, net
Non-cash impairment losses, long-lived assets	$ 95			$ 446					$ 541
Common Units
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 (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
Cash distributions per common unit (in dollars per unit)	$ 0.18	$ 0.18	$ 0.18	$ 0.36	$ 0.36	$ 0.36	$ 0.36	$ 0.30	$ 0.90	$ 1.38