Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting [Abstract]
Number of reportable operating segments (in segments) | segment			3
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	$ 258,013	$ 264,185	$ 540,620	$ 520,033
Corporate-level property management expenses	(8,646)	(8,469)	(17,405)	(16,898)
Depreciation and amortization	(133,609)	(119,465)	(265,168)	(240,033)
General and administrative	(14,952)	(13,927)	(28,934)	(27,386)
Expensed acquisition and investment related costs	(15)	(24)	(102)	(56)
Gain on sale of real estate and land	16,597	0	16,597	0
Interest expense	(54,447)	(54,112)	(109,594)	(107,755)
Total return swap income	2,788	1,975	4,772	4,020
Interest and other income	11,405	8,347	6,184	20,608
Equity income from co-investments	17,257	16,959	38,554	33,235
Deferred tax expense on unrealized gain on unconsolidated co-investment	(1,636)	0	(1,636)	0
(Loss) gain on early retirement of debt, net	(5,027)	332	(4,706)	1,668
Gain on remeasurement of co-investment	0	0	234,694	31,535
Net income	90,076	98,061	418,841	223,566
Net reportable operating segment - real estate assets	11,094,024		11,094,024		$ 10,348,660
Real estate under development	467,915		467,915		546,075
Co-investments	1,008,758		1,008,758		1,335,339
Real estate held for sale, net	24,495		24,495		0
Cash and cash equivalents, including restricted cash	256,475	54,971	256,475	54,971	81,094	$ 151,395
Marketable securities	154,433		154,433		144,193
Notes and other receivables	44,748		44,748		134,365
Operating lease right-of-use assets	73,669		73,669		74,744
Prepaid expenses and other assets	52,894		52,894		40,935
Total assets	13,177,411		13,177,411		12,705,405
Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	368,149	359,375	757,899	713,263
Management and Other Fees From Affiliates Income
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	2,348	2,260	4,965	4,595
Operating Segments | Southern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	99,307	109,260	210,404	217,256
Net reportable operating segment - real estate assets	4,160,950		4,160,950		4,233,110
Operating Segments | Southern California | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	143,983	152,415	299,625	303,878
Operating Segments | Northern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	110,649	101,887	228,909	201,743
Net reportable operating segment - real estate assets	5,491,288		5,491,288		4,408,404
Operating Segments | Northern California | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	153,831	136,427	313,846	271,185
Operating Segments | Seattle Metro
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	40,780	43,512	85,206	84,680
Net reportable operating segment - real estate assets	1,429,957		1,429,957		1,456,187
Operating Segments | Seattle Metro | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	60,649	60,240	123,693	119,890
Other real estate assets
Revenues from External Customers and Long-Lived Assets [Line Items]
Net operating income	7,277	9,526	16,101	16,354
Net reportable operating segment - real estate assets	11,829		11,829		$ 250,959
Other real estate assets | Rental and Other Property Revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 9,686	$ 10,293	$ 20,735	$ 18,310