Organization and Basis of Presentation (Summary of Interest Held in Properties) (Details)	Sep. 30, 2017 mall community_center
Consolidated properties
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Development, Malls (mall) | mall	0
Expansions, Malls (mall) | mall	1
Redevelopments, Malls (mall) | mall	1
Unconsolidated Properties
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Development, Community Centers (community center) | community_center	1
Expansions, Community Centers (community center) | community_center	0
Redevelopments, Community Centers (community center) | community_center	0