Reportable Segments - NOI for Each Segment from Our Rental Real Estate Specific to Continuing Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Rental income	$ 623,206	$ 622,433	$ 1,818,867	$ 1,958,270
Operating income	521,554	182,410	1,033,958	961,384
Total Assets	20,663,015		20,663,015		$ 20,286,891
Capital Expenditures			107,706
Same Store
Segment Reporting Information [Line Items]
Rental income	601,852	600,252	1,758,176	1,870,199
Operating expenses	206,583	202,164	612,705	593,502
Operating income	395,269	398,088	1,145,471	1,276,697
Total Assets	18,156,651		18,156,651
Capital Expenditures			106,130
Non-same store/other
Segment Reporting Information [Line Items]
Rental income	21,354	22,181	60,691	88,071
Operating expenses	6,787	6,174	26,336	27,874
Operating income	14,567	16,007	34,355	60,197
Total Assets	2,506,364		2,506,364
Capital Expenditures			1,576
Same Store, Non-same Store and Other
Segment Reporting Information [Line Items]
Rental income	623,206	622,433	1,818,867	1,958,270
Operating expenses	213,370	208,338	639,041	621,376
Operating income	409,836	414,095	1,179,826	1,336,894
Los Angeles | Same Store
Segment Reporting Information [Line Items]
Rental income	117,542	112,201	337,153	346,599
Operating expenses	36,929	36,783	109,997	108,594
Operating income	80,613	75,418	227,156	238,005
Total Assets	2,926,617		2,926,617
Capital Expenditures			13,959
Orange County | Same Store
Segment Reporting Information [Line Items]
Rental income	28,264	26,229	80,773	79,241
Operating expenses	6,480	6,457	18,937	18,539
Operating income	21,784	19,772	61,836	60,702
Total Assets	375,365		375,365
Capital Expenditures			4,124
San Diego | Same Store
Segment Reporting Information [Line Items]
Rental income	20,282	18,637	58,211	56,001
Operating expenses	4,735	4,652	13,920	13,684
Operating income	15,547	13,985	44,291	42,317
Total Assets	234,733		234,733
Capital Expenditures			2,060
Subtotal - Southern California | Same Store
Segment Reporting Information [Line Items]
Rental income	166,088	157,067	476,137	481,841
Operating expenses	48,144	47,892	142,854	140,817
Operating income	117,944	109,175	333,283	341,024
Total Assets	3,536,715		3,536,715
Capital Expenditures			20,143
San Francisco | Same Store
Segment Reporting Information [Line Items]
Rental income	102,166	109,908	302,043	346,089
Operating expenses	31,542	30,913	93,983	90,849
Operating income	70,624	78,995	208,060	255,240
Total Assets	3,264,017		3,264,017
Capital Expenditures			15,853
Washington D.C. | Same Store
Segment Reporting Information [Line Items]
Rental income	100,019	103,160	298,165	311,119
Operating expenses	34,397	32,979	99,369	95,799
Operating income	65,622	70,181	198,796	215,320
Total Assets	3,270,172		3,270,172
Capital Expenditures			20,392
New York | Same Store
Segment Reporting Information [Line Items]
Rental income	103,015	98,333	299,320	324,866
Operating expenses	49,939	49,915	152,228	148,145
Operating income	53,076	48,418	147,092	176,721
Total Assets	3,902,715		3,902,715
Capital Expenditures			22,641
Boston | Same Store
Segment Reporting Information [Line Items]
Rental income	58,864	59,527	171,871	182,502
Operating expenses	19,504	18,601	57,041	53,727
Operating income	39,360	40,926	114,830	128,775
Total Assets	1,710,489		1,710,489
Capital Expenditures			15,766
Seattle | Same Store
Segment Reporting Information [Line Items]
Rental income	61,888	62,748	181,908	195,198
Operating expenses	20,117	18,972	58,616	55,845
Operating income	41,771	43,776	123,292	139,353
Total Assets	1,975,574		1,975,574
Capital Expenditures			10,234
Denver | Same Store
Segment Reporting Information [Line Items]
Rental income	9,812	9,509	28,732	28,584
Operating expenses	2,940	2,892	8,614	8,320
Operating income	6,872	6,617	20,118	20,264
Total Assets	496,969		496,969
Capital Expenditures			1,101
Non-same store | Non-same store/other
Segment Reporting Information [Line Items]
Rental income	16,563	2,481	28,581	11,440
Operating expenses	6,777	539	10,916	2,534
Operating income	9,786	1,942	17,665	8,906
Total Assets	1,484,091		1,484,091
Capital Expenditures			659
Other | Non-same store/other
Segment Reporting Information [Line Items]
Rental income	4,791	19,700	32,110	76,631
Operating expenses	10	5,635	15,420	25,340
Operating income	4,781	$ 14,065	16,690	$ 51,291
Total Assets	$ 1,022,273		1,022,273
Capital Expenditures			$ 917