Business Segments (Details Textual)	6 Months Ended
	Jun. 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	121
Number of apartment homes in apartment communities | apartment_home	32,796
Wholly And Partially Owned Consolidated Properties [Member] | Same Store [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	94
Number of apartment homes in apartment communities | apartment_home	27,876
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	19
Number of apartment homes in apartment communities | apartment_home	2,399
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