Investments in Real Estate Entities (Details) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended				9 Months Ended			1 Months Ended
	Sep. 30, 2012 home	Sep. 30, 2011	Sep. 30, 2012 home	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 Fund I and II	Dec. 31, 2011 Fund I and II	Sep. 30, 2012 Fund I	Sep. 30, 2012 AvalonBay Value Added Fund II, L.P	Sep. 30, 2012 Unconsolidated real estate entities entity	Sep. 30, 2012 Unconsolidated real estate entities Minimum	Sep. 30, 2012 Unconsolidated real estate entities Maximum	Jul. 31, 2012 Avalon Del Rey home
Investment in Real Estate Entities
Number of apartment homes included in joint venture apartment communities owned	53,487		53,487										309
Ownership interest acquired (as a percent)													30.00%
Repayment of secured debt													$ 43,606,000
Acquisition of joint venture partner additional equity interest			3,350,000	6,570,000									67,200,000
Ownership additional interest acquired (as a percent)													70.00%
Promoted interest in unconsolidated equities													4,055,000
Gain on acquisition of unconsolidated entity	14,194,000		14,194,000										14,194,000
Number of unconsolidated real estate entities										4
Ownership interest percentage											15.20%	31.30%
Assets:
Real estate, net	1,477,756,000		1,477,756,000		1,583,397,000
Other assets	88,627,000		88,627,000		70,233,000
Total assets	1,566,383,000		1,566,383,000		1,653,630,000
Liabilities and partners' capital:
Mortgage notes payable and credit facility	1,033,226,000		1,033,226,000		1,074,429,000
Other liabilities	26,379,000		26,379,000		27,335,000
Partners' capital	506,778,000		506,778,000		551,866,000
Total liabilities and partners' capital	1,566,383,000		1,566,383,000		1,653,630,000
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	43,168,000	40,953,000	130,300,000	117,407,000
Operating and other expenses	(18,733,000)	(18,829,000)	(56,533,000)	(53,474,000)
Gain on sale of communities	44,723,000	12,445,000	57,457,000	12,445,000
Interest expense, net	(12,742,000)	(12,818,000)	(38,468,000)	(37,596,000)
Depreciation expense	(11,947,000)	(12,363,000)	(37,244,000)	(35,702,000)
Net income	44,469,000	9,388,000	55,512,000	3,080,000
Costs in excess of equity in underlying net assets of the respective investments						8,305,000	9,167,000
Maximum amount that will be paid for capital contributions made by partners (as a percent)						10.00%
Maximum amount that will be paid for capital contributions made by partners								7,500,000	8,910,000
Abandoned Pursuit Costs and Impairment of Long-Lived Assets
Expensed costs related to abandoned pursuits	608,000	633,000	1,749,000	2,636,000
Aggregate charge of other than temporary impairment		$ 14,052,000		$ 14,052,000