Reportable Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Rental income:
Same store	$ 626,746	$ 602,046	$ 1,239,506	$ 1,191,430
Segment Reporting Segment Non Same Store Rental Income	23,020	12,498	40,985	18,099
Segment Reporting Information Revenues	649,766	614,544	1,280,491	1,117,106
Operating expenses:
Same store	208,086	205,213	426,227	416,591
Segment Reporting Segment Non Same Store Operating Expenses	10,912	7,061	22,556	18,525
Segment Reporting Segment Operating Expenses	218,998	212,274	448,783	398,387
NOI:
Same store	418,660	396,833	813,279	774,839
Segment Reporting Information Non Same Store Net Operating Income	12,108	5,437	18,429	(426)
Segment Reporting Information Net Operating Income	430,768	402,270	831,708	718,719
Assets	22,991,402		22,991,402		22,834,545
Payments to Acquire Other Property, Plant, and Equipment			76,912
Reportable Segments (Textuals) [Abstract]
Units in same store properties			100,648
Rental income	649,766	614,544	1,280,491	1,117,106
Property Repairs and Maintenance	(115,388)	(113,501)	(240,961)	(212,030)
Real Estate Taxes and Insurance	(83,055)	(76,742)	(165,149)	(141,837)
Property management	(20,555)	(22,031)	(42,673)	(44,520)
Total Operating Expenses	(218,998)	(212,274)	(448,783)	(398,387)
Archstone [Member]
Reportable Segments (Textuals) [Abstract]
Units in same store properties			18,465
Same Store [Domain]
NOI:
Assets	20,029,692		20,029,692
Payments to Acquire Other Property, Plant, and Equipment			74,398
Non-same store [Domain]
NOI:
Assets	2,961,710		2,961,710
Payments to Acquire Other Property, Plant, and Equipment			2,514
Boston [Domain]
Rental income:
Same store	63,117	61,401	125,024	120,455
Segment Reporting Segment Non Same Store Rental Income	790	898	1,817	1,154
Operating expenses:
Same store	19,259	19,444	41,414	39,651
Segment Reporting Segment Non Same Store Operating Expenses	202	201	413	255
NOI:
Same store	43,858	41,957	83,610	80,804
Segment Reporting Information Non Same Store Net Operating Income	588	697	1,404	899
Boston [Domain] | Same Store [Domain]
NOI:
Assets	1,953,627		1,953,627
Payments to Acquire Other Property, Plant, and Equipment			8,814
Boston [Domain] | Non-same store [Domain]
NOI:
Assets	48,830		48,830
Payments to Acquire Other Property, Plant, and Equipment			630
Denver [Domain]
Rental income:
Same store	27,511	25,524	54,123	50,494
Operating expenses:
Same store	7,648	7,770	15,098	14,987
NOI:
Same store	19,863	17,754	39,025	35,507
Denver [Domain] | Same Store [Domain]
NOI:
Assets	530,832		530,832
Payments to Acquire Other Property, Plant, and Equipment			1,904
New York [Domain]
Rental income:
Same store	114,221	109,299	225,407	217,297
Operating expenses:
Same store	41,898	40,634	88,102	83,745
NOI:
Same store	72,323	68,665	137,305	133,552
New York [Domain] | Same Store [Domain]
NOI:
Assets	4,720,592		4,720,592
Payments to Acquire Other Property, Plant, and Equipment			8,202
San Francisco [Domain]
Rental income:
Same store	84,082	77,514	165,343	152,459
Operating expenses:
Same store	26,305	25,955	52,960	54,109
NOI:
Same store	57,777	51,559	112,383	98,350
San Francisco [Domain] | Same Store [Domain]
NOI:
Assets	2,753,902		2,753,902
Payments to Acquire Other Property, Plant, and Equipment			12,704
Seattle [Domain]
Rental income:
Same store	38,977	36,176	76,702	71,548
Segment Reporting Segment Non Same Store Rental Income	2,756	1,271	4,444	1,303
Operating expenses:
Same store	13,037	12,316	25,805	24,553
Segment Reporting Segment Non Same Store Operating Expenses	1,042	373	1,779	374
NOI:
Same store	25,940	23,860	50,897	46,995
Segment Reporting Information Non Same Store Net Operating Income	1,714	898	2,665	929
Seattle [Domain] | Same Store [Domain]
NOI:
Assets	1,046,051		1,046,051
Payments to Acquire Other Property, Plant, and Equipment			5,264
Seattle [Domain] | Non-same store [Domain]
NOI:
Assets	226,604		226,604
Payments to Acquire Other Property, Plant, and Equipment			281
South Florida [Domain]
Rental income:
Same store	49,456	47,051	97,893	93,289
Segment Reporting Segment Non Same Store Rental Income	1,241	14	2,041	24
Operating expenses:
Same store	18,220	17,774	36,404	35,417
Segment Reporting Segment Non Same Store Operating Expenses	760	68	1,301	146
NOI:
Same store	31,236	29,277	61,489	57,872
Segment Reporting Information Non Same Store Net Operating Income	481	(54)	740	(122)
South Florida [Domain] | Same Store [Domain]
NOI:
Assets	1,170,295		1,170,295
Payments to Acquire Other Property, Plant, and Equipment			7,600
South Florida [Domain] | Non-same store [Domain]
NOI:
Assets	70,896		70,896
Payments to Acquire Other Property, Plant, and Equipment			16
Southern California [Domain]
Rental income:
Same store	104,608	100,156	207,272	198,366
Segment Reporting Segment Non Same Store Rental Income	8,446	4,106	15,623	5,397
Operating expenses:
Same store	34,811	34,275	69,450	69,149
Segment Reporting Segment Non Same Store Operating Expenses	4,261	1,976	7,452	2,593
NOI:
Same store	69,797	65,881	137,822	129,217
Segment Reporting Information Non Same Store Net Operating Income	4,185	2,130	8,171	2,804
Southern California [Domain] | Same Store [Domain]
NOI:
Assets	2,978,750		2,978,750
Payments to Acquire Other Property, Plant, and Equipment			11,953
Southern California [Domain] | Non-same store [Domain]
NOI:
Assets	511,343		511,343
Payments to Acquire Other Property, Plant, and Equipment			645
Washington DC [Domain]
Rental income:
Same store	111,739	112,815	222,135	223,807
Segment Reporting Segment Non Same Store Rental Income	5,906	3,512	10,840	5,320
Operating expenses:
Same store	35,102	35,165	72,499	71,049
Segment Reporting Segment Non Same Store Operating Expenses	1,954	1,209	3,857	1,862
NOI:
Same store	76,637	77,650	149,636	152,758
Segment Reporting Information Non Same Store Net Operating Income	3,952	2,303	6,983	3,458
Washington DC [Domain] | Same Store [Domain]
NOI:
Assets	4,270,418		4,270,418
Payments to Acquire Other Property, Plant, and Equipment			14,834
Washington DC [Domain] | Non-same store [Domain]
NOI:
Assets	306,594		306,594
Payments to Acquire Other Property, Plant, and Equipment			852
Non-Core [Domain]
Rental income:
Same store	33,035	32,110	65,607	63,715
Operating expenses:
Same store	11,806	11,880	24,495	23,931
NOI:
Same store	21,229	20,230	41,112	39,784
Non-Core [Domain] | Same Store [Domain]
NOI:
Assets	605,225		605,225
Payments to Acquire Other Property, Plant, and Equipment			3,123
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	3,881	2,697	6,220	4,901
Operating expenses:
Segment Reporting Segment Non Same Store Operating Expenses	2,693	3,234	7,754	13,295
NOI:
Segment Reporting Information Non Same Store Net Operating Income	1,188	(537)	(1,534)	(8,394)
Other [Domain] | Non-same store [Domain]
NOI:
Assets	1,797,443		1,797,443
Payments to Acquire Other Property, Plant, and Equipment			$ 90