Reportable Segments - NOI for Each Segment from Our Rental Real Estate Specific to Continuing Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Rental income	$ 598,059	$ 653,532	$ 1,195,661	$ 1,335,837
Operating income	376,844	356,889	512,404	778,974
Total Assets	20,464,346		20,464,346		$ 20,286,891
Capital Expenditures			66,443
Same Store
Segment Reporting Information [Line Items]
Rental income	589,008	634,393	1,174,563	1,288,732
Operating expenses	201,207	193,920	410,940	395,952
Operating income	387,801	440,473	763,623	892,780
Total Assets	18,571,806		18,571,806
Capital Expenditures			65,943
Non-same store/other
Segment Reporting Information [Line Items]
Rental income	9,051	19,139	21,098	47,105
Operating expenses	3,940	5,570	14,731	17,086
Operating income	5,111	13,569	6,367	30,019
Total Assets	1,892,540		1,892,540
Capital Expenditures			500
Same Store, Non-same Store and Other
Segment Reporting Information [Line Items]
Rental income	598,059	653,532	1,195,661	1,335,837
Operating expenses	205,147	199,490	425,671	413,038
Operating income	392,912	454,042	769,990	922,799
Los Angeles | Same Store
Segment Reporting Information [Line Items]
Rental income	113,639	118,686	226,592	241,570
Operating expenses	36,769	35,841	74,889	73,626
Operating income	76,870	82,845	151,703	167,944
Total Assets	3,052,015		3,052,015
Capital Expenditures			8,232
Orange County | Same Store
Segment Reporting Information [Line Items]
Rental income	26,669	26,318	52,510	53,013
Operating expenses	6,122	5,910	12,458	12,083
Operating income	20,547	20,408	40,052	40,930
Total Assets	380,069		380,069
Capital Expenditures			2,372
San Diego | Same Store
Segment Reporting Information [Line Items]
Rental income	19,188	18,587	37,928	37,365
Operating expenses	4,545	4,447	9,185	9,033
Operating income	14,643	14,140	28,743	28,332
Total Assets	237,670		237,670
Capital Expenditures			1,427
Subtotal - Southern California | Same Store
Segment Reporting Information [Line Items]
Rental income	159,496	163,591	317,030	331,948
Operating expenses	47,436	46,198	96,532	94,742
Operating income	112,060	117,393	220,498	237,206
Total Assets	3,669,754		3,669,754
Capital Expenditures			12,031
San Francisco | Same Store
Segment Reporting Information [Line Items]
Rental income	104,285	121,106	209,617	246,209
Operating expenses	31,759	30,593	65,034	62,389
Operating income	72,526	90,513	144,583	183,820
Total Assets	3,442,539		3,442,539
Capital Expenditures			10,443
Washington DC | Same Store
Segment Reporting Information [Line Items]
Rental income	99,030	103,241	198,147	207,958
Operating expenses	31,651	30,717	64,973	62,819
Operating income	67,379	72,524	133,174	145,139
Total Assets	3,291,944		3,291,944
Capital Expenditures			13,108
New York | Same Store
Segment Reporting Information [Line Items]
Rental income	98,271	110,230	196,304	226,532
Operating expenses	49,834	47,908	102,288	98,230
Operating income	48,437	62,322	94,016	128,302
Total Assets	3,951,560		3,951,560
Capital Expenditures			13,956
Boston | Same Store
Segment Reporting Information [Line Items]
Rental income	57,777	60,711	113,714	123,673
Operating expenses	18,512	17,087	37,719	35,275
Operating income	39,265	43,624	75,995	88,398
Total Assets	1,726,284		1,726,284
Capital Expenditures			9,067
Seattle | Same Store
Segment Reporting Information [Line Items]
Rental income	60,574	66,096	120,831	133,338
Operating expenses	19,372	18,778	38,720	37,070
Operating income	41,202	47,318	82,111	96,268
Total Assets	1,987,663		1,987,663
Capital Expenditures			6,723
Denver | Same Store
Segment Reporting Information [Line Items]
Rental income	9,575	9,418	18,920	19,074
Operating expenses	2,643	2,639	5,674	5,427
Operating income	6,932	6,779	13,246	13,647
Total Assets	502,062		502,062
Capital Expenditures			615
Non-same store | Non-same store/other
Segment Reporting Information [Line Items]
Rental income	4,589	2,190	10,499	7,374
Operating expenses	1,755	298	3,506	1,611
Operating income	2,834	1,892	6,993	5,763
Total Assets	663,201		663,201
Capital Expenditures			288
Other | Non-same store/other
Segment Reporting Information [Line Items]
Rental income	4,462	16,949	10,599	39,731
Operating expenses	2,185	5,272	11,225	15,475
Operating income	2,277	$ 11,677	(626)	$ 24,256
Total Assets	$ 1,229,339		1,229,339
Capital Expenditures			$ 212