Acquisitions (Narrative) (Details) (USD $) In Millions	Sep. 30, 2011	Feb. 28, 2011 Non-Controlling Owners' Interest [Member] Magellan Crude Oil LLC [Member]	Sep. 30, 2011 2011 Acquisitions [Member]
Business Acquisition [Line Items]
Acquisition of interest		$ 40.5	$ 17.8
Changes in purchase price allocation from Property, plant and equipment to Goodwill	13.3
Changes in fair value of purchase price allocation for inactive pipeline	$ 0