Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
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	$ 241,264	$ 258,013	$ 483,661	$ 540,620
Corporate-level property management expenses	(9,105)	(8,646)	(18,052)	(17,405)
Depreciation and amortization	(128,736)	(133,609)	(257,323)	(265,168)
General and administrative	(12,222)	(14,952)	(22,034)	(28,934)
Expensed acquisition and investment related costs	(41)	(15)	(56)	(102)
Gain on sale of real estate and land	0	16,597	100,096	16,597
Interest expense	(50,971)	(54,447)	(102,620)	(109,594)
Total return swap income	2,633	2,788	5,477	4,772
Interest and other income	22,371	11,405	36,758	6,184
Equity income from co-investments	18,248	17,257	35,259	38,554
Deferred tax expense on unrealized gain on unconsolidated co-investment	(1,842)	(1,636)	(2,350)	(1,636)
Loss on early retirement of debt, net	(16,465)	(5,027)	(18,982)	(4,706)
Gain on remeasurement of co-investment	2,260	0	2,260	234,694
Net income	69,615	90,076	246,564	418,841
Net reportable operating segment - real estate assets	10,904,751		10,904,751		$ 10,927,786
Real estate under development	208,330		208,330		386,047
Co-investments	1,037,270		1,037,270		1,018,010
Real estate held for sale	0		0		57,938
Cash and cash equivalents, including restricted cash	58,176	256,475	58,176	256,475	84,041	$ 81,094
Marketable securities	175,782		175,782		147,768
Notes and other receivables	238,855		238,855		195,104
Operating lease right-of-use assets	70,551		70,551		72,143
Prepaid expenses and other assets	53,484		53,484		47,340
Total assets	12,747,199		12,747,199		12,936,177
Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	348,757	368,149	701,633	757,899
Management and Other Fees From Affiliates Income
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	2,221	2,348	4,470	4,965
Operating Segments | Southern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	99,263	96,829	198,514	205,118
Net reportable operating segment - real estate assets	3,985,599		3,985,599		3,993,275
Operating Segments | Southern California | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	143,230	140,510	286,242	292,405
Operating Segments | Northern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	98,916	109,592	200,541	226,779
Net reportable operating segment - real estate assets	5,527,443		5,527,443		5,408,019
Operating Segments | Northern California | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	143,386	152,118	290,076	310,574
Operating Segments | Seattle Metro
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	40,386	40,780	79,165	85,206
Net reportable operating segment - real estate assets	1,377,702		1,377,702		1,403,678
Operating Segments | Seattle Metro | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	59,267	60,649	117,900	123,693
Other real estate assets
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	2,699	10,812	5,441	23,517
Net reportable operating segment - real estate assets	14,007		14,007		$ 122,814
Other real estate assets | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 2,874	$ 14,872	$ 7,415	$ 31,227