Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)	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	$ 245,289	$ 256,069	$ 728,950	$ 796,689
Corporate-level property management expenses	(9,068)	(8,619)	(27,120)	(26,024)
Depreciation and amortization	(130,564)	(130,202)	(387,887)	(395,370)
General and administrative	(12,712)	(13,310)	(34,746)	(42,244)
Expensed acquisition and investment related costs	(108)	(2)	(164)	(104)
Gain on sale of real estate and land	42,897	22,654	142,993	39,251
Interest expense	(50,019)	(55,430)	(152,639)	(165,024)
Total return swap income	2,660	2,977	8,137	7,749
Interest and other income	11,998	6,512	48,756	12,696
Equity income from co-investments	25,433	14,960	60,692	53,514
Deferred tax expense on unrealized gain on unconsolidated co-investment	(3,041)	0	(5,391)	(1,636)
Loss on early retirement of debt, net	0	(19,114)	(18,982)	(23,820)
Gain on remeasurement of co-investment	0	0	2,260	234,694
Net income (loss)	125,002	78,842	371,566	497,683
Net reportable operating segment - real estate assets	10,903,431		10,903,431		$ 10,927,786
Real estate under development	212,426		212,426		386,047
Co-investments	1,081,861		1,081,861		1,018,010
Real estate held for sale	0		0		57,938
Cash and cash equivalents, including restricted cash	60,952	569,075	60,952	569,075	84,041	$ 81,094
Marketable securities	183,140		183,140		147,768
Notes and other receivables	213,985		213,985		195,104
Operating lease right-of-use assets	69,756		69,756		72,143
Prepaid expenses and other assets	63,090		63,090		47,340
Total assets	12,788,641		12,788,641		12,936,177
Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	360,620	368,464	1,062,253	1,126,363
Management and Other Fees From Affiliates Income
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	2,237	2,347	6,707	7,312
Operating Segments | Southern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	103,660	91,639	300,761	295,402
Net reportable operating segment - real estate assets	3,949,224		3,949,224		3,981,650
Operating Segments | Southern California | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	150,807	136,651	434,926	426,987
Operating Segments | Northern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	98,948	102,559	299,489	329,338
Net reportable operating segment - real estate assets	5,489,918		5,489,918		5,408,019
Operating Segments | Northern California | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	145,807	147,081	435,883	457,655
Operating Segments | Seattle Metro
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	39,876	41,216	119,041	126,422
Net reportable operating segment - real estate assets	1,369,129		1,369,129		1,403,678
Operating Segments | Seattle Metro | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	60,280	60,617	178,180	184,310
Other real estate assets
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	2,805	20,655	9,659	45,527
Net reportable operating segment - real estate assets	95,160		95,160		$ 134,439
Other real estate assets | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 3,726	$ 24,115	$ 13,264	$ 57,411