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Real Estate Acquisitions and Dispositions (Details) - USD ($) $ in Millions		3 Months Ended
	Sep. 25, 2018	Mar. 31, 2018
Outlets at Orange
Acquisitions
Ownership interests acquired (as a percent)	50.00%
Outlets at Orange \| Mortgage Maturing April 1, 2024
Acquisitions
Fixed mortgage loan	$ 215.0
Fixed rate of interest	4.22%
Outlets at Orange \| Simon Property Group, L.P.
Acquisitions
Number of units issued in connection with acquisition of the remaining interest in orange outlet	475,183
Consideration for the acquisition	$ 84.1
Consolidated properties \| Retail properties \| Disposed of by Sales And Means Other than Sale
Dispositions
Nets gains on disposition		$ 135.3
Consolidated properties \| Retail properties \| Disposed of by Sales And Means Other than Sale \| Non-recourse $200M Mortgage
Dispositions
Non-recourse mortgage		$ 200.0