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Revenues - Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) community	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Disaggregation of Revenue [Line Items]
Rental and other property	$ 389,750	$ 353,888
Management and other fees from affiliates	2,617	2,335
Total revenues	$ 392,367	356,223
Occupancy threshold for classification as stabilized	90.00%
Apartment communities owned (in communities) \| community	250
Deferred revenue	$ 3,700		$ 3,900
Deferred revenue, revenue recognized	200
Deferred revenue balance from contracts with remaining performance obligations	3,700
Rental income
Disaggregation of Revenue [Line Items]
Rental and other property	383,498	347,805
Other property
Disaggregation of Revenue [Line Items]
Rental and other property	6,252	6,083
Rental and other property revenues
Disaggregation of Revenue [Line Items]
Rental and other property	389,750	353,888
Rental and other property revenues \| Same-property
Disaggregation of Revenue [Line Items]
Rental and other property	346,456	335,658
Rental and other property revenues \| Acquisitions
Disaggregation of Revenue [Line Items]
Rental and other property	21,924	987
Rental and other property revenues \| Development
Disaggregation of Revenue [Line Items]
Rental and other property	4,075	1,158
Rental and other property revenues \| Redevelopment
Disaggregation of Revenue [Line Items]
Rental and other property	5,401	5,229
Rental and other property revenues \| Non-residential/other, net
Disaggregation of Revenue [Line Items]
Rental and other property	$ 11,894	10,856
Apartment communities owned (in communities) \| community	3
Rental and other property revenues \| Operating Segments \| Southern California
Disaggregation of Revenue [Line Items]
Rental and other property	$ 155,642	151,463
Rental and other property revenues \| Operating Segments \| Northern California
Disaggregation of Revenue [Line Items]
Rental and other property	164,079	136,745
Rental and other property revenues \| Operating Segments \| Seattle Metro
Disaggregation of Revenue [Line Items]
Rental and other property	63,844	60,413
Rental and other property revenues \| Other real estate assets
Disaggregation of Revenue [Line Items]
Rental and other property	$ 6,185	$ 5,267