Investments in Real Estate Entities (Details 2) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Assets:
Real estate, net	$ 2,067,969,000		$ 2,067,969,000		$ 1,337,084,000
Other assets	168,822,000		168,822,000		73,252,000
Total assets	2,236,791,000		2,236,791,000		1,410,336,000
Liabilities and partners' capital:
Mortgage notes payable and credit facility	1,372,106,000		1,372,106,000		943,259,000
Other liabilities	40,860,000		40,860,000		20,405,000
Partners' capital	823,825,000		823,825,000		446,672,000
Total liabilities and partners' capital	2,236,791,000		2,236,791,000		1,410,336,000
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	57,452,000	44,505,000	101,216,000	87,132,000
Operating and other expenses	(22,986,000)	(19,131,000)	(40,680,000)	(37,800,000)
Gain on sale of communities	11,216,000	3,825,000	65,267,000	12,735,000
Interest expense, net	(15,829,000)	(12,659,000)	(31,098,000)	(25,726,000)
Depreciation expense	(17,783,000)	(12,597,000)	(30,933,000)	(25,297,000)
Net income (loss)	12,070,000	3,943,000	63,772,000	11,044,000
Impairment of investment in an unconsolidated entities	0	0	0	0
Impairment loss	0	0	0	0
Abandoned Pursuit Costs and Impairment of Long-lived Assets
Expensed costs related to abandoned pursuits	195,000	820,000	440,000	968,000
Fund I and II
Combined summary of the operating results of the accounted for using the equity method
Costs in excess of equity in underlying net assets of the respective investments	6,430,000		6,430,000		7,342,000
Maximum amount that will be paid for capital contributions made by partners (as a percent)			10.00%
AvalonBay Value Added Fund, L.P.
Combined summary of the operating results of the accounted for using the equity method
Maximum amount that will be paid for capital contributions made by partners	7,500,000		7,500,000
AvalonBay Value Added Fund II, L.P
Combined summary of the operating results of the accounted for using the equity method
Maximum amount that will be paid for capital contributions made by partners	$ 8,910,000		$ 8,910,000