Segment Reporting (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting
Total revenue	$ 580,774	$ 567,404	$ 1,693,653	$ 1,745,459
NOI	382,687	363,712	1,107,475	1,157,740
Gross real estate	24,376,310	23,221,488	24,376,310	23,221,488
Real estate assets held for sale, net	89,529		89,529
Operating Segments | Established
Segment Reporting
Total revenue	519,797	513,418	1,520,420	1,586,405
NOI	347,694	347,158	1,023,057	1,108,837
Gross real estate	20,100,815	19,954,294	20,100,815	19,954,294
Operating Segments | Established | New England
Segment Reporting
Total revenue	77,037	75,394	224,614	231,478
NOI	48,115	48,290	142,278	152,589
Gross real estate	2,781,806	2,756,835	2,781,806	2,756,835
Operating Segments | Established | Metro NY/NJ
Segment Reporting
Total revenue	108,776	106,542	319,079	325,807
NOI	72,564	72,283	215,147	225,793
Gross real estate	4,129,121	4,102,402	4,129,121	4,102,402
Operating Segments | Established | Mid-Atlantic
Segment Reporting
Total revenue	85,328	84,974	252,271	261,932
NOI	56,103	56,721	168,359	182,503
Gross real estate	3,575,978	3,550,373	3,575,978	3,550,373
Operating Segments | Established | Southeast Florida
Segment Reporting
Total revenue	8,152	6,950	23,099	21,818
NOI	5,026	3,331	13,772	11,755
Gross real estate	395,594	393,594	395,594	393,594
Operating Segments | Established | Denver, Colorado
Segment Reporting
Total revenue	6,070	5,422	17,576	15,758
NOI	4,011	3,418	11,965	10,084
Gross real estate	320,214	319,038	320,214	319,038
Operating Segments | Established | Pacific Northwest
Segment Reporting
Total revenue	28,092	27,545	81,640	84,808
NOI	19,197	18,913	55,389	59,977
Gross real estate	1,057,166	1,051,451	1,057,166	1,051,451
Operating Segments | Established | Northern California
Segment Reporting
Total revenue	90,127	97,777	270,124	308,522
NOI	63,088	71,207	190,658	232,470
Gross real estate	3,458,280	3,430,831	3,458,280	3,430,831
Operating Segments | Established | Southern California
Segment Reporting
Total revenue	116,215	108,814	332,017	336,282
NOI	79,590	72,995	225,489	233,666
Gross real estate	4,382,656	4,349,770	4,382,656	4,349,770
Operating Segments | Other Stabilized
Segment Reporting
Total revenue	27,908	22,316	77,034	64,962
NOI	18,217	14,238	49,796	42,251
Gross real estate	1,528,196	1,125,829	1,528,196	1,125,829
Operating Segments | Development / Redevelopment
Segment Reporting
Total revenue	28,543	6,943	65,543	17,119
NOI	16,776	2,316	34,622	6,652
Gross real estate	2,401,751	1,698,823	2,401,751	1,698,823
Operating Segments | Disposals
Segment Reporting
Gross real estate		720,432		720,432
Land Held for Future Development
Segment Reporting
Gross real estate	66,769	43,494	66,769	43,494
Non-allocated
Segment Reporting
Total revenue	695	419	2,380	1,109
Gross real estate	278,779	399,048	278,779	399,048
Continuing Operations
Segment Reporting
Total revenue	576,943	543,096	1,665,377	1,669,595
Continuing Operations | Operating Segments | Established
Segment Reporting
Total revenue	519,797	513,418	1,520,420	1,586,405
Continuing Operations | Operating Segments | Other Stabilized
Segment Reporting
Total revenue	27,908	22,316	77,034	64,962
Continuing Operations | Non-allocated
Segment Reporting
Total revenue	$ 695	$ 419	$ 2,380	$ 1,109