Organization and Basis of Presentation - Interest Held in Properties (Details)	Sep. 30, 2018 mall other_property
Consolidated Properties
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Development, Malls | mall	0
Redevelopments, Malls | mall	8
Development, All Other | other_property	0
Redevelopments, All Other | other_property	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 | other_property	2
Redevelopments, All Other | other_property	0