Organization, Formation and Structure (Details)	Sep. 30, 2017 partnership property
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Distribution of REIT taxable income (excluding net capital gains) to its stockholders (percent)	90.00%
Number of partnerships | partnership	2
Shopping Centers
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of real estate properties	49
Mixed-Use Properties
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of real estate properties	6
Non-operating Development Properties
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of real estate properties	3