Investments in Real Estate Entities (Details 2) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Assets:
Real estate, net	$ 2,053,602,000		$ 2,053,602,000		$ 1,337,084,000
Other assets	100,304,000		100,304,000		73,252,000
Total assets	2,153,906,000		2,153,906,000		1,410,336,000
Liabilities and partners' capital:
Mortgage notes payable and credit facility	1,358,891,000		1,358,891,000		943,259,000
Other liabilities	47,717,000		47,717,000		20,405,000
Partners' capital	747,298,000		747,298,000		446,672,000
Total liabilities and partners' capital	2,153,906,000		2,153,906,000		1,410,336,000
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	56,240,000	43,168,000	157,456,000	130,300,000
Operating and other expenses	(22,866,000)	(18,733,000)	(63,575,000)	(56,533,000)
Gain on sale of communities	5,395,000	44,723,000	70,662,000	57,457,000
Interest expense, net	(15,376,000)	(12,742,000)	(46,474,000)	(38,468,000)
Depreciation expense	(15,668,000)	(11,947,000)	(46,602,000)	(37,244,000)
Net income	7,725,000	44,469,000	71,467,000	55,512,000
Impairment of investment in an unconsolidated entities	0	0	0	0
Impairment loss	0	0	0	0
Expensed Acquisition, Development and Other Pursuit Costs and Impairment of Long-Lived Assets
Expensed costs related to acquisition, development and other pursuit costs and impairment of long-lived assets	351,000	608,000	792,000	1,749,000
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	6,237,000		6,237,000		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