Investments in Partially Owned Entities - Consolidated Variable Interest Entities ("VIEs") - Additional Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) Property ApartmentUnit	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Variable Interest Entity [Line Items]
Properties | Property	307
Apartment units | ApartmentUnit	79,322
Total assets	$ 20,663,015		$ 20,286,891
Total liabilities	$ 9,329,432		9,184,454
Number of unconsolidated land parcel acquired | Property	2
Aggregate gross purchase price to acquire land parcels	$ 1,022,275	$ 48,898
Unconsolidated Joint Venture [Member]
Variable Interest Entity [Line Items]
Aggregate gross purchase price to acquire land parcels	55,400
Equity Residential [Member]
Variable Interest Entity [Line Items]
Aggregate gross purchase price to acquire land parcels	$ 21,800
Consolidated VIE [Member]
Variable Interest Entity [Line Items]
Properties | Property	17
Apartment units | ApartmentUnit	3,774
Total assets	$ 839,300		784,100
Total liabilities	$ 247,900		$ 224,000