Reportable Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Rental income:
Same store	$ 613,878	$ 590,452
Segment Reporting Segment Non Same Store Rental Income	16,847	4,533
Segment Reporting Information Revenues	630,725	502,562
Operating expenses:
Same store	218,239	211,485
Segment Reporting Segment Non Same Store Operating Expenses	11,546	11,357
Segment Reporting Segment Operating Expenses	229,785	186,113
NOI:
Same store	395,639	378,967
Segment Reporting Information Non Same Store Net Operating Income	5,301	(6,824)
Segment Reporting Information Net Operating Income	400,940	316,449
Assets	22,889,631		22,834,545
Payments to Acquire Other Property, Plant, and Equipment	32,191
Reportable Segments (Textuals) [Abstract]
Units in same store properties	100,984
Rental income	630,725	502,562
Property Repairs and Maintenance	(125,573)	(98,529)
Real Estate Taxes and Insurance	(82,094)	(65,095)
Property management	(22,118)	(22,489)
Total Operating Expenses	(229,785)	(186,113)
Archstone [Member]
Reportable Segments (Textuals) [Abstract]
Units in same store properties	18,465
Same Store [Domain]
NOI:
Assets	20,174,187
Payments to Acquire Other Property, Plant, and Equipment	31,146
Non-same store [Domain]
NOI:
Assets	2,715,444
Payments to Acquire Other Property, Plant, and Equipment	1,045
Boston [Domain]
Rental income:
Same store	61,907	59,054
Segment Reporting Segment Non Same Store Rental Income	1,028	256
Operating expenses:
Same store	22,154	20,207
Segment Reporting Segment Non Same Store Operating Expenses	211	53
NOI:
Same store	39,753	38,847
Segment Reporting Information Non Same Store Net Operating Income	817	203
Boston [Domain] | Same Store [Domain]
NOI:
Assets	1,968,613
Payments to Acquire Other Property, Plant, and Equipment	4,078
Boston [Domain] | Non-same store [Domain]
NOI:
Assets	48,971
Payments to Acquire Other Property, Plant, and Equipment	263
Denver [Domain]
Rental income:
Same store	26,611	24,970
Operating expenses:
Same store	7,449	7,217
NOI:
Same store	19,162	17,753
Denver [Domain] | Same Store [Domain]
NOI:
Assets	536,226
Payments to Acquire Other Property, Plant, and Equipment	762
New York [Domain]
Rental income:
Same store	111,185	107,997
Operating expenses:
Same store	46,202	43,111
NOI:
Same store	64,983	64,886
New York [Domain] | Same Store [Domain]
NOI:
Assets	4,727,805
Payments to Acquire Other Property, Plant, and Equipment	3,051
San Francisco [Domain]
Rental income:
Same store	81,261	74,945
Operating expenses:
Same store	26,655	28,156
NOI:
Same store	54,606	46,789
San Francisco [Domain] | Same Store [Domain]
NOI:
Assets	2,769,826
Payments to Acquire Other Property, Plant, and Equipment	5,716
Seattle [Domain]
Rental income:
Same store	37,725	35,372
Segment Reporting Segment Non Same Store Rental Income	1,687	25
Operating expenses:
Same store	12,768	12,237
Segment Reporting Segment Non Same Store Operating Expenses	690	1
NOI:
Same store	24,957	23,135
Segment Reporting Information Non Same Store Net Operating Income	997	24
Seattle [Domain] | Same Store [Domain]
NOI:
Assets	1,053,600
Payments to Acquire Other Property, Plant, and Equipment	2,205
Seattle [Domain] | Non-same store [Domain]
NOI:
Assets	190,041
Payments to Acquire Other Property, Plant, and Equipment	160
South Florida [Domain]
Rental income:
Same store	48,437	46,239
Segment Reporting Segment Non Same Store Rental Income	800	14
Operating expenses:
Same store	18,184	17,643
Segment Reporting Segment Non Same Store Operating Expenses	466	78
NOI:
Same store	30,253	28,596
Segment Reporting Information Non Same Store Net Operating Income	334	(64)
South Florida [Domain] | Same Store [Domain]
NOI:
Assets	1,178,426
Payments to Acquire Other Property, Plant, and Equipment	3,119
South Florida [Domain] | Non-same store [Domain]
NOI:
Assets	70,725
Payments to Acquire Other Property, Plant, and Equipment	(1)
Southern California [Domain]
Rental income:
Same store	102,665	98,210
Segment Reporting Segment Non Same Store Rental Income	7,174	1,292
Operating expenses:
Same store	34,347	34,587
Segment Reporting Segment Non Same Store Operating Expenses	3,122	617
NOI:
Same store	68,318	63,623
Segment Reporting Information Non Same Store Net Operating Income	4,052	675
Southern California [Domain] | Same Store [Domain]
NOI:
Assets	3,000,465
Payments to Acquire Other Property, Plant, and Equipment	5,142
Southern California [Domain] | Non-same store [Domain]
NOI:
Assets	446,912
Payments to Acquire Other Property, Plant, and Equipment	173
Washington DC [Domain]
Rental income:
Same store	110,396	110,993
Segment Reporting Segment Non Same Store Rental Income	4,934	1,806
Operating expenses:
Same store	37,396	35,884
Segment Reporting Segment Non Same Store Operating Expenses	1,863	653
NOI:
Same store	73,000	75,109
Segment Reporting Information Non Same Store Net Operating Income	3,071	1,153
Washington DC [Domain] | Same Store [Domain]
NOI:
Assets	4,299,085
Payments to Acquire Other Property, Plant, and Equipment	5,529
Washington DC [Domain] | Non-same store [Domain]
NOI:
Assets	305,668
Payments to Acquire Other Property, Plant, and Equipment	449
Non-Core [Domain]
Rental income:
Same store	33,691	32,672
Operating expenses:
Same store	13,084	12,443
NOI:
Same store	20,607	20,229
Non-Core [Domain] | Same Store [Domain]
NOI:
Assets	640,141
Payments to Acquire Other Property, Plant, and Equipment	1,544
Archstone pre-ownership [Member]
Rental income:
Same store	0	(92,423)
Operating expenses:
Same store	0	(36,729)
NOI:
Same store	0	(55,694)
Other [Domain]
Rental income:
Segment Reporting Segment Non Same Store Rental Income	1,224	1,140
Operating expenses:
Segment Reporting Segment Non Same Store Operating Expenses	5,194	9,955
NOI:
Segment Reporting Information Non Same Store Net Operating Income	(3,970)	(8,815)
Other [Domain] | Non-same store [Domain]
NOI:
Assets	1,653,127
Payments to Acquire Other Property, Plant, and Equipment	$ 1