Segment Reporting (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting
Total revenue	$ 551,135	$ 602,267
NOI	364,655	415,513
Gross real estate	24,060,003	23,272,507
Real Estate Held-For-Sale, Gross	75,814
Operating Segments | Established
Segment Reporting
Total revenue	502,258	552,633
NOI	339,670	395,020
Gross real estate	20,198,860	20,087,827
Operating Segments | Established | New England
Segment Reporting
Total revenue	73,318	78,845
NOI	46,267	52,269
Gross real estate	2,768,546	2,748,893
Operating Segments | Established | Metro NY/NJ
Segment Reporting
Total revenue	104,949	112,813
NOI	71,640	79,653
Gross real estate	4,113,854	4,100,221
Operating Segments | Established | Mid-Atlantic
Segment Reporting
Total revenue	82,931	90,345
NOI	56,291	65,210
Gross real estate	3,562,330	3,537,207
Operating Segments | Established | Southeast Florida
Segment Reporting
Total revenue	7,241	7,504
NOI	4,189	4,126
Gross real estate	394,451	393,025
Operating Segments | Established | Denver, Colorado
Segment Reporting
Total revenue	5,653	5,170
NOI	4,019	3,340
Gross real estate	319,667	318,624
Operating Segments | Established | Pacific Northwest
Segment Reporting
Total revenue	30,669	33,480
NOI	20,666	24,306
Gross real estate	1,232,975	1,225,511
Operating Segments | Established | Northern California
Segment Reporting
Total revenue	90,406	106,877
NOI	64,063	81,879
Gross real estate	3,443,896	3,425,170
Operating Segments | Established | Southern California
Segment Reporting
Total revenue	107,091	117,599
NOI	72,535	84,237
Gross real estate	4,363,141	4,339,176
Operating Segments | Other Stabilized
Segment Reporting
Total revenue	29,993	28,585
NOI	18,464	18,396
Gross real estate	1,279,134	1,260,482
Operating Segments | Development / Redevelopment
Segment Reporting
Total revenue	15,704	4,789
NOI	6,521	2,097
Gross real estate	2,041,887	1,413,772
Operating Segments | Disposals [Member]
Segment Reporting
Gross real estate		435,561
Land Held for Future Development
Segment Reporting
Gross real estate	184,058	38,115
Non-allocated
Segment Reporting
Total revenue	877	1,007
Gross real estate	356,064	472,311
Continuing Operations
Segment Reporting
Total revenue	548,832	587,014
Continuing Operations | Operating Segments | Established
Segment Reporting
Total revenue	502,258	552,633
Continuing Operations | Operating Segments | Other Stabilized
Segment Reporting
Total revenue	29,993	28,585
Continuing Operations | Non-allocated
Segment Reporting
Total revenue	$ 877	$ 1,007