Investments in Real Estate Entities (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013 item community	Feb. 27, 2013
Investments in Archstone Unconsolidated Entities
Number of land parcels	4
Archstone
Investments in Archstone Unconsolidated Entities
Equity interest held (as a percent)		40.00%
Archstone | Archstone U.S. Fund
Investments in Archstone Unconsolidated Entities
Number of communities owned	9
Number of apartment homes in communities owned	1,726
Number of marina communities	1
Number of boat slips	229
Equity interest held (as a percent)		28.60%
Number of outstanding unsecured loans	9
Debt outstanding	$ 327,849,000
Archstone | AC JV
Investments in Archstone Unconsolidated Entities
Number of communities owned	2
Number of apartment homes in communities owned	818
Number of apartment homes in communities for development	301
Equity interest held (as a percent)		20.00%
Number of outstanding unsecured loans	8
Debt outstanding	162,300,000
Archstone | AC JV | Maximum
Investments in Archstone Unconsolidated Entities
Maximum geographic radius for existing assets within considered for right of first offer	1
Archstone | Brandywine
Investments in Archstone Unconsolidated Entities
Number of apartment homes in communities owned	305
Equity interest held (as a percent)	28.70%	26.10%
Debt outstanding	24,839,000
Number of members who hold various interests in the joint venture	5
Additional interest purchased	2.60%
Archstone | SWIB
Investments in Archstone Unconsolidated Entities
Number of communities owned	6
Number of apartment homes in communities owned	1,902
Equity interest held (as a percent)	20.00%
Number of outstanding unsecured loans	2
Debt outstanding	$ 187,021,000
Ownership interest held by subsidiaries of the entity (as a percent)	40.00%
Number of land parcels	2