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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Rental income	$ 622,433	$ 685,120	$ 1,958,270	$ 2,016,796
Operating income	182,410	368,338	961,384	947,232
Total Assets	20,623,978		20,623,978		$ 21,172,769
Capital Expenditures			92,123
Same Store
Segment Reporting Information [Line Items]
Rental income	603,097	652,330	1,854,383	1,900,820
Operating expenses	203,158	196,863	586,707	576,070
Operating income	399,939	455,467	1,267,676	1,324,750
Total Assets	17,947,180		17,947,180
Capital Expenditures			89,807
Non-same store/other
Segment Reporting Information [Line Items]
Rental income	19,336	32,790	103,887	115,976
Operating expenses	5,180	5,649	34,669	32,861
Operating income	14,156	27,141	69,218	83,115
Total Assets	2,676,798		2,676,798
Capital Expenditures			2,316
Same Store, Non-same Store and Other
Segment Reporting Information [Line Items]
Rental income	622,433	685,120	1,958,270	2,016,796
Operating expenses	208,338	202,512	621,376	608,931
Operating income	414,095	482,608	1,336,894	1,407,865
Los Angeles | Same Store
Segment Reporting Information [Line Items]
Rental income	115,208	122,506	355,122	363,258
Operating expenses	37,023	36,461	108,953	108,606
Operating income	78,185	86,045	246,169	254,652
Total Assets	3,034,765		3,034,765
Capital Expenditures			17,008
Orange County | Same Store
Segment Reporting Information [Line Items]
Rental income	26,229	26,635	79,241	78,522
Operating expenses	6,535	6,351	18,702	18,493
Operating income	19,694	20,284	60,539	60,029
Total Assets	392,632		392,632
Capital Expenditures			5,056
San Diego | Same Store
Segment Reporting Information [Line Items]
Rental income	23,581	24,064	71,430	71,088
Operating expenses	6,358	6,468	18,776	18,595
Operating income	17,223	17,596	52,654	52,493
Total Assets	377,663		377,663
Capital Expenditures			2,834
Subtotal - Southern California | Same Store
Segment Reporting Information [Line Items]
Rental income	165,018	173,205	505,793	512,868
Operating expenses	49,916	49,280	146,431	145,694
Operating income	115,102	123,925	359,362	367,174
Total Assets	3,805,060		3,805,060
Capital Expenditures			24,898
San Francisco | Same Store
Segment Reporting Information [Line Items]
Rental income	113,246	122,706	346,766	354,142
Operating expenses	31,349	30,453	89,557	87,117
Operating income	81,897	92,253	257,209	267,025
Total Assets	3,259,452		3,259,452
Capital Expenditures			11,789
Washington DC | Same Store
Segment Reporting Information [Line Items]
Rental income	99,569	101,771	294,029	295,107
Operating expenses	32,253	31,347	90,974	90,124
Operating income	67,316	70,424	203,055	204,983
Total Assets	3,092,477		3,092,477
Capital Expenditures			15,890
New York | Same Store
Segment Reporting Information [Line Items]
Rental income	100,076	118,803	325,920	348,190
Operating expenses	50,179	48,614	148,306	144,197
Operating income	49,897	70,189	177,614	203,993
Total Assets	3,948,417		3,948,417
Capital Expenditures			16,571
Boston | Same Store
Segment Reporting Information [Line Items]
Rental income	58,830	64,039	182,502	188,710
Operating expenses	18,461	17,840	53,603	53,478
Operating income	40,369	46,199	128,899	135,232
Total Assets	1,774,255		1,774,255
Capital Expenditures			13,137
Seattle | Same Store
Segment Reporting Information [Line Items]
Rental income	60,216	65,370	186,030	188,093
Operating expenses	19,073	17,569	54,125	51,884
Operating income	41,143	47,801	131,905	136,209
Total Assets	1,818,213		1,818,213
Capital Expenditures			7,010
Denver | Same Store
Segment Reporting Information [Line Items]
Rental income	6,142	6,436	13,343	13,710
Operating expenses	1,927	1,760	3,711	3,576
Operating income	4,215	4,676	9,632	10,134
Total Assets	249,306		249,306
Capital Expenditures			512
Non-same store | Non-same store/other
Segment Reporting Information [Line Items]
Rental income	19,236	9,538	87,404	33,683
Operating expenses	6,136	2,856	27,122	10,351
Operating income	13,100	6,682	60,282	23,332
Total Assets	1,679,594		1,679,594
Capital Expenditures			1,811
Other | Non-same store/other
Segment Reporting Information [Line Items]
Rental income	100	23,252	16,483	82,293
Operating expenses	(956)	2,793	7,547	22,510
Operating income	1,056	$ 20,459	8,936	$ 59,783
Total Assets	$ 997,204		997,204
Capital Expenditures			$ 505