Net Income Per Limited Partner Unit (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net Income Per Limited Partner Unit
General partner ownership interest (as a percent)			2.00%
Basic Net Income per Limited Partner Unit
Net income attributable to Plains	$ 378	$ 225	$ 609	$ 408
Less: General partner's incentive distribution	(69)	(52)	(134)	(103)
Less: General partner 2% ownership	(6)	(3)	(10)	(6)
Net income available to limited partners	303	170	465	299
Less: Undistributed earnings allocated and distributions to participating securities	(2)		(3)
Net income available to limited partners in accordance with the application of the two-class method for MLPs	$ 301	$ 170	$ 462	$ 299
Basic weighted average number of limited partner units outstanding (in units)	162	149	159	146
Basic net income per limited partner unit (in dollars per unit)	$ 1.86	$ 1.14	$ 2.90	$ 2.04