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Real Estate Acquisitions and Dispositions (Details) - USD ($) $ in Millions			9 Months Ended
	Sep. 19, 2019	Sep. 25, 2018	Sep. 30, 2018
Hotel
Acquisitions
Ownership interests acquired (as a percent)	50.00%
Consideration for the acquisition	$ 12.8
Hotel \| Mortgage bearing 4.02%
Acquisitions
Fixed mortgage loan	$ 21.5
Fixed rate of interest	4.02%
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			$ 144.9
Consolidated properties \| Retail properties \| Disposed of by Sales And Means Other than Sale \| Non-recourse $200M Mortgage
Dispositions
Non-recourse mortgage			$ 200.0