Revenues - Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) community	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) community	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Disaggregation of Revenue [Line Items]
Rental and other property	$ 368,149	$ 359,375	$ 757,899	$ 713,263
Management and other fees from affiliates	2,348	2,260	4,965	4,595
Total revenues	$ 370,497	361,635	$ 762,864	717,858
Occupancy threshold for classification as stabilized	90.00%		90.00%
Apartment communities owned (in communities) | community	248		248
Deferred revenue	$ 3,500		$ 3,500		$ 3,900
Deferred revenue, revenue recognized			400
Deferred revenue balance from contracts with remaining performance obligations	3,500		3,500
Rental income
Disaggregation of Revenue [Line Items]
Rental and other property	363,087	353,167	746,585	700,972
Other property
Disaggregation of Revenue [Line Items]
Rental and other property	5,062	6,208	11,314	12,291
Rental and other property revenues
Disaggregation of Revenue [Line Items]
Rental and other property	368,149	359,375	757,899	713,263
Rental and other property revenues | Same-property
Disaggregation of Revenue [Line Items]
Rental and other property	323,651	336,492	668,287	670,387
Rental and other property revenues | Acquisitions
Disaggregation of Revenue [Line Items]
Rental and other property	19,885	475	38,764	475
Rental and other property revenues | Development
Disaggregation of Revenue [Line Items]
Rental and other property	4,420	1,217	8,495	2,375
Rental and other property revenues | Redevelopment
Disaggregation of Revenue [Line Items]
Rental and other property	5,096	5,240	10,497	10,469
Rental and other property revenues | Non-residential/other, net
Disaggregation of Revenue [Line Items]
Rental and other property	$ 15,097	15,951	$ 31,856	29,557
Apartment communities owned (in communities) | community	3		3
Rental and other property revenues | Operating Segments | Southern California
Disaggregation of Revenue [Line Items]
Rental and other property	$ 143,983	152,415	$ 299,625	303,878
Rental and other property revenues | Operating Segments | Northern California
Disaggregation of Revenue [Line Items]
Rental and other property	153,831	136,427	313,846	271,185
Rental and other property revenues | Operating Segments | Seattle Metro
Disaggregation of Revenue [Line Items]
Rental and other property	60,649	60,240	123,693	119,890
Rental and other property revenues | Other real estate assets
Disaggregation of Revenue [Line Items]
Rental and other property	$ 9,686	$ 10,293	$ 20,735	$ 18,310