Partners' Capital and Distributions (Changes In Limited Partner Units Outstanding) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Capital Unit [Line Items]
Amount Authorized Under Equity Distribution Agreement		$ 750.0
Limited Partners' Capital Account [Roll Forward]
Limited partner unitholders, units outstanding		227,783,916	227,427,247	227,068,257
Partners' Capital Account, Units, Unit-based Compensation		216,679	350,552	354,529
Limited partner unitholders, units outstanding		228,024,556	227,783,916	227,427,247
Limited Partners' Capital Account, Right to Receive Distribution in Cash, Period		45 days
Limited Partners' Capital Account, Removal of Magellan GP, LLC, Percentage Vote		100.00%
Limited Partners' Capital Account, Annual Report Available, Period		120 days
Limited Partners' Capital Account, Tax Reporting Information, Period		90 days
Management [Member]
Limited Partners' Capital Account [Roll Forward]
Partners' Capital Account, Units, Unit-based Compensation		216,679	350,552	354,529
Director [Member]
Limited Partners' Capital Account [Roll Forward]
Partners' Capital Account, Units, Unit-based Compensation	[1]	23,961	6,117	4,461

[1] Limited partner units issued to settle the equity-based retainer paid to independent directors of our general partner.