Business Segments (Details Textual)	9 Months Ended
	Sep. 30, 2019 Property apartment_home Segment office_building
Business Segments (Textual) [Abstract]
Number of reportable segments | Segment	4
Wholly And Partially Owned Consolidated Properties [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	124
Number of apartment homes in apartment communities | apartment_home	33,682
Wholly And Partially Owned Consolidated Properties [Member] | Same Store [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	95
Number of apartment homes in apartment communities | apartment_home	27,640
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	7
Number of apartment homes in apartment communities | apartment_home	3,137
Wholly And Partially Owned Consolidated Properties [Member] | Acquisition [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	7
Number of apartment homes in apartment communities | apartment_home	1,590
Wholly And Partially Owned Consolidated Properties [Member] | Other Real Estate [Member]
Business Segments (Textual) [Abstract]
Number of owned and managed apartment communities in segments | Property	15
Number of apartment homes in apartment communities | apartment_home	1,315
Wholly And Partially Owned Consolidated Properties [Member] | 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