Commitments and Contingencies - Additional Information (Details) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2021 Agreement	Sep. 30, 2021 USD ($) Property ApartmentUnit Agreement
Commitments and Contingencies [Line Items]
Number of consolidated projects in various stages of development		2
Consolidated wholly owned projects in various stages of development		1
Consolidated partially owned projects in various stages of development		1
Number of unconsolidated projects in various stages of development		2
Number of consolidated projects in lease-up		2
Partially owned consolidated projects in lease-up		1
Wholly owned consolidated projects in lease-up		1
Units in various stages of development | ApartmentUnit		1,441
Consolidated project under development commitment fund | $		$ 328.8
Various stages of development with estimated completion dates ranging through Jun 30, 2024		Jun. 30, 2024
Number of joint venture agreement | Agreement		2
Number of joint venture agreement completed | Agreement	1
Number of joint venture agreement currently under construction | Agreement		1
Number of unconsolidated joint venture agreements | Agreement		2
Equity method investment period		3 years
Percentage of expected non-recourse construction debt		60.00%
Initial minimum co-investment of combined equity | $		$ 750.0
Equity Residential [Member]
Commitments and Contingencies [Line Items]
Ownership Percentage		75.00%
Toll Brothers Inc. [Member]
Commitments and Contingencies [Line Items]
Ownership Percentage		25.00%