Segment Reporting (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting
Real Estate Held-For-Sale, Gross	$ 41,866
Total revenue	601,651	$ 566,184
NOI	424,535	394,917
Gross real estate	23,708,068	22,262,363
Operating Segments | Established
Segment Reporting
Total revenue	547,956	531,829
NOI	391,645	380,337
Gross real estate	19,377,124	19,183,244
Operating Segments | Established | New England
Segment Reporting
Total revenue	81,669	78,688
NOI	53,680	52,083
Gross real estate	2,765,270	2,717,130
Operating Segments | Established | Metro NY/NJ
Segment Reporting
Total revenue	120,731	118,377
NOI	84,484	82,984
Gross real estate	4,343,033	4,311,202
Operating Segments | Established | Mid-Atlantic
Segment Reporting
Total revenue	91,717	88,370
NOI	66,309	62,916
Gross real estate	3,545,582	3,507,734
Operating Segments | Established | Pacific Northwest
Segment Reporting
Total revenue	28,736	27,802
NOI	20,838	20,210
Gross real estate	991,802	986,190
Operating Segments | Established | Northern California
Segment Reporting
Total revenue	104,360	101,261
NOI	80,451	78,715
Gross real estate	3,268,787	3,248,903
Operating Segments | Established | Southern California
Segment Reporting
Total revenue	114,810	111,466
NOI	82,455	79,916
Gross real estate	4,142,235	4,092,527
Operating Segments | Established | Expansion Markets [Member]
Segment Reporting
Total revenue	5,933	5,865
NOI	3,428	3,513
Gross real estate	320,415	319,558
Operating Segments | Other Stabilized
Segment Reporting
Total revenue	35,491	22,027
NOI	23,496	14,729
Gross real estate	1,591,348	1,171,127
Operating Segments | Development / Redevelopment
Segment Reporting
Total revenue	15,773	549
NOI	9,394	(149)
Gross real estate	2,220,386	1,130,302
Operating Segments | Disposals [Member]
Segment Reporting
Gross real estate		285,943
Land Held for Future Development
Segment Reporting
Gross real estate	38,115	104,963
Non-allocated
Segment Reporting
Total revenue	1,007	1,139
Gross real estate	481,095	672,727
Continuing Operations
Segment Reporting
Total revenue	600,227	555,544
Continuing Operations | Operating Segments | Established
Segment Reporting
Total revenue	547,956	531,829
Continuing Operations | Operating Segments | Other Stabilized
Segment Reporting
Total revenue	35,491	22,027
Continuing Operations | Non-allocated
Segment Reporting
Total revenue	$ 1,007	$ 1,139