Business Segments (Details Textual)	9 Months Ended
	Sep. 30, 2020 Property apartment_home Segment office_building
Business Segments (Textual) [Abstract]
Number of reportable segments | Segment	3
Wholly And Partially Owned Consolidated Properties [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	122
Number of apartment homes in apartment communities | apartment_home	33,067
Wholly And Partially Owned Consolidated Properties [Member] | Same Store [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	93
Number of apartment homes in apartment communities | apartment_home	27,610
Wholly And Partially Owned Consolidated Properties [Member] | Redevelopment and Development [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	8
Number of apartment homes in apartment communities | apartment_home	2,521
Wholly And Partially Owned Consolidated Properties [Member] | Acquisition and Other Real Estate [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	20
Number of apartment homes in apartment communities | apartment_home	2,670
Wholly And Partially Owned Consolidated Properties [Member] | Acquisition and Other Real Estate [Member] | Office Building [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | office_building	1
Unconsolidated Properties [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	4
Number of apartment homes in apartment communities | apartment_home	142