Commitments and Contingencies - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) Property ApartmentUnit
Accrual for environmental loss contingencies | $	$ 5.2
Number of properties with environmental reserves | Property	3
Loss contingency accrual | $	$ 0.9
Projects in various stages of development | Property	3
Units in various stages of development | ApartmentUnit	443
Consolidated project under development commitment fund | $	$ 105.2
Various stages of development with estimated completion dates ranging through December 31, 2019	Dec. 31, 2019
Partially Owned Properties – Unconsolidated
Number of unconsolidated projects | Property	2