Business - Additional Information (Details)	12 Months Ended
	Dec. 31, 2018 State Property ApartmentUnit	Apr. 02, 2018 ApartmentUnit	Feb. 01, 2018 ApartmentUnit
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Number of states in which entity operates | State	11
Properties | Property	307
Apartment units	79,482
Number of operating properties under long-term ground leases | Property	14
Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Long term ground lease expiration period	2042
Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Long term ground lease expiration period	2113
Master-Leased Properties – Consolidated | Boston
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Number of self managed apartments			94
Master-Leased Properties – Consolidated | Los Angeles
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Number of self managed apartments		597
ERPOP [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Noncontrolling interest, ownership percentage by parent	96.40%