Organization and Basis of Presentation (Summary of Interest Held in Properties) (Details)	Mar. 31, 2018 associated_center mall community_center
Consolidated properties
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Development, Malls (mall)	0
Redevelopments, Malls (mall)	6
Development, All Other (properties) | community_center	1
Redevelopments, All Other (properties) | associated_center	0
Unconsolidated Properties
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Development, Malls (mall)	0
Redevelopments, Malls (mall)	1
Development, All Other (properties) | community_center	2
Redevelopments, All Other (properties) | community_center	0