Investments in Partially Owned Entities - Consolidated Variable Interest Entities ("VIEs") - Additional Information (Details) $ in Thousands	Sep. 30, 2020 USD ($) Property ApartmentUnit	Dec. 31, 2019 USD ($)
Variable Interest Entity [Line Items]
Properties | Property	305
Apartment units | ApartmentUnit	78,568
Total assets	$ 20,623,978	$ 21,172,769
Total liabilities	$ 9,575,906	10,164,843
Consolidated VIE [Member]
Variable Interest Entity [Line Items]
Properties | Property	16
Apartment units | ApartmentUnit	3,399
Total assets	$ 764,200	754,700
Total liabilities	$ 210,200	$ 323,100