Reportable Segments - NOI for Each Segment from Our Rental Real Estate Specific to Continuing Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Rental income	$ 682,305	$ 662,302
Operating income	422,109	209,969
Total Assets	20,919,318		$ 21,172,769
Capital Expenditures	38,342
Same Store
Segment Reporting Information [Line Items]
Rental income	648,377	631,099
Operating expenses	199,937	195,224
Operating income	448,440	435,875
Total Assets	18,503,975
Capital Expenditures	37,657
Non-same store/other
Segment Reporting Information [Line Items]
Rental income	33,928	31,203
Operating expenses	13,611	11,288
Operating income	20,317	19,915
Total Assets	2,415,343
Capital Expenditures	685
Same Store, Non-same Store and Other
Segment Reporting Information [Line Items]
Rental income	682,305	662,302
Operating expenses	213,548	206,512
Operating income	468,757	455,790
Los Angeles | Same Store
Segment Reporting Information [Line Items]
Rental income	121,920	119,536
Operating expenses	36,916	36,430
Operating income	85,004	83,106
Total Assets	3,090,294
Capital Expenditures	9,360
Orange County | Same Store
Segment Reporting Information [Line Items]
Rental income	26,694	25,828
Operating expenses	6,214	6,175
Operating income	20,480	19,653
Total Assets	401,249
Capital Expenditures	2,021
San Diego | Same Store
Segment Reporting Information [Line Items]
Rental income	24,142	23,304
Operating expenses	6,317	6,148
Operating income	17,825	17,156
Total Assets	385,989
Capital Expenditures	1,117
Subtotal - Southern California | Same Store
Segment Reporting Information [Line Items]
Rental income	172,756	168,668
Operating expenses	49,447	48,753
Operating income	123,309	119,915
Total Assets	3,877,532
Capital Expenditures	12,498
San Francisco | Same Store
Segment Reporting Information [Line Items]
Rental income	121,950	118,071
Operating expenses	30,694	29,502
Operating income	91,256	88,569
Total Assets	3,362,398
Capital Expenditures	4,121
Washington DC | Same Store
Segment Reporting Information [Line Items]
Rental income	103,884	101,504
Operating expenses	32,044	31,520
Operating income	71,840	69,984
Total Assets	3,343,974
Capital Expenditures	6,836
New York | Same Store
Segment Reporting Information [Line Items]
Rental income	116,590	114,761
Operating expenses	50,932	48,894
Operating income	65,658	65,867
Total Assets	4,001,406
Capital Expenditures	6,327
Boston | Same Store
Segment Reporting Information [Line Items]
Rental income	63,683	61,920
Operating expenses	18,160	18,241
Operating income	45,523	43,679
Total Assets	1,809,524
Capital Expenditures	5,665
Seattle | Same Store
Segment Reporting Information [Line Items]
Rental income	64,956	61,598
Operating expenses	17,427	17,118
Operating income	47,529	44,480
Total Assets	1,855,378
Capital Expenditures	2,026
Denver | Same Store
Segment Reporting Information [Line Items]
Rental income	4,558	4,577
Operating expenses	1,233	1,196
Operating income	3,325	3,381
Total Assets	253,763
Capital Expenditures	184
Non-same store | Non-same store/other
Segment Reporting Information [Line Items]
Rental income	29,653	5,838
Operating expenses	9,165	1,783
Operating income	20,488	4,055
Total Assets	1,660,327
Capital Expenditures	548
Other | Non-same store/other
Segment Reporting Information [Line Items]
Rental income	4,275	25,365
Operating expenses	4,446	9,505
Operating income	(171)	$ 15,860
Total Assets	755,016
Capital Expenditures	$ 137