Information with Respect to Stock Options Granted under the 1994 Stock Option and Incentive Plan (the "1994 Plan") and under the AvalonBay Communities, Inc. 2009 Stock Option and Incentive Plan (the "2009 Plan") (Detail) (USD $)	9 Months Ended
	Sep. 30, 2011
Options outstanding
Exercised	(813,707)
Granted	144,827
Stock Option and Incentive Plan 2009
Options outstanding
Options outstanding beginning balance	126,484
Exercised	(18,487)
Granted	144,827
Options outstanding ending balance	252,824
Options exercisable ending balance	26,138
Weighted-Average Exercise Price
Options outstanding Weighted-Average Exercise Price beginning balance	$ 74.20
Exercised	$ 74.20
Granted	$ 115.83
Options outstanding Weighted-Average Exercise Price ending balance	$ 98.05
Options exercisable Weighted-Average Exercise Price ending balance	$ 74.20
Stock Option and Incentive Plan 1994
Options outstanding
Options outstanding beginning balance	2,072,217
Exercised	(795,220)
Forfeited	(21,653)
Options outstanding ending balance	1,255,344
Options exercisable ending balance	1,148,381
Weighted-Average Exercise Price
Options outstanding Weighted-Average Exercise Price beginning balance	$ 88.50
Exercised	$ 82.86
Forfeited	$ 43.29
Options outstanding Weighted-Average Exercise Price ending balance	$ 92.86
Options exercisable Weighted-Average Exercise Price ending balance	$ 96.98