Summary of Activity of 2003 Stock Plan and 2006 Equity Incentive Plan (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Options Outstanding, Number of Shares
Beginning Balance	4,641,039
Granted	896,381
Exercised	(179,273)
Canceled	(60,636)
Ending Balance	5,297,511
Options Outstanding, Price per Share Range
Beginning Balance, lower limit	$ 0.35
Beginning Balance, upper limit	$ 6.74
Granted, lower limit	$ 1.40
Granted, upper limit	$ 1.75
Exercised, lower limit	$ 0.35
Exercised, upper limit	$ 0.82
Canceled, lower limit	$ 0.65
Canceled, upper limit	$ 5.50
Ending Balance, lower limit	$ 0.35
Ending Balance, upper limit	$ 6.74
Options Outstanding, Weighted Average Exercise Price
Beginning Balance	$ 2.23
Granted	$ 1.67
Exercised	$ 0.36
Canceled	$ 1.91
Ending Balance	$ 2.20
Options Outstanding, Aggregate Intrinsic Value	$ 1,177,163	[1]	$ 1,509,270	[1]
Options Exercisable, Number of Shares	3,575,182		3,206,994
Options Exercisable, Weighted Average Exercise Price	$ 2.37		$ 2.23
Options Exercisable, Aggregate Intrinsic Value	$ 1,016,110	[1]	$ 1,258,740	[1]

[1] The intrinsic value of an option represents the amount by which the market value of the stock exceeds the exercise price of the option of in-the-money options only. The aggregate intrinsic value is based on the closing price of our Common Stock on the NASDAQ Capital Market, as applicable, on the respective dates.