Segment Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) segment	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of reportable segments | segment	3
Number of operating segments | segment	3
Net operating income	$ 298,349	$ 289,244
Management and other fees from affiliates	2,713	2,765
Corporate-level property management expenses	(11,731)	(11,432)
Depreciation and amortization	(139,733)	(136,347)
General and administrative	(17,171)	(15,311)
Expensed acquisition and investment related costs	(68)	(339)
Casualty loss	0	(433)
Gain on sale of real estate and land	0	59,238
Interest expense	(55,933)	(51,045)
Total return swap income	796	1,033
Interest and other income	57,275	12,450
Equity income from co-investments	12,366	10,871
Tax (expense) benefit on unconsolidated co-investments	(49)	900
Gain on remeasurement of co-investment	138,326	0
Net income	285,140	161,594
Net reportable operating segment - real estate assets	10,869,727		$ 10,470,292
Real estate under development	24,631		23,724
Co-investments	1,062,575		1,061,733
Cash and cash equivalents, including restricted cash	507,870	77,158	400,334	$ 42,681
Marketable securities	91,295		87,795
Notes and other receivables	183,040		174,621
Operating lease right-of-use assets	62,858		63,757
Prepaid expenses and other assets	83,189		79,171
Total assets	12,885,185		12,361,427
Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	424,215	409,656
Management and other fees from affiliates
Revenues from External Customers and Long-Lived Assets [Line Items]
Management and other fees from affiliates	2,713	2,765
Operating Segments | Southern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	124,333	116,942
Net reportable operating segment - real estate assets	4,208,556		3,802,648
Operating Segments | Southern California | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	176,002	166,877
Operating Segments | Northern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	115,679	114,555
Net reportable operating segment - real estate assets	5,192,173		5,242,343
Operating Segments | Northern California | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	168,839	163,728
Operating Segments | Seattle Metro
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	50,916	49,894
Net reportable operating segment - real estate assets	1,376,656		1,333,030
Operating Segments | Seattle Metro | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	71,913	70,038
Other real estate assets
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	7,421	7,853
Net reportable operating segment - real estate assets	92,342		$ 92,271
Other real estate assets | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 7,461	$ 9,013