Commitments and Contingencies - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) Property ApartmentUnit
Accrual for environmental loss contingencies | $	$ 4.3
Number of properties with environmental reserves	3
Projects in various stages of development	3
Units in various stages of development | ApartmentUnit	691
Consolidated project under development commitment fund | $	$ 388.4
Various stages of development with estimated completion dates ranging through September 30, 2021	Sep. 30, 2021
Partially Owned Properties - Unconsolidated
Number of unconsolidated projects	2