Summary Information about Options Outstanding (Detail) (USD $)	6 Months Ended
	Jun. 30, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 0.94
Range of Exercise Prices, upper limit	$ 10.74
Options Number Outstanding	3,269,947
Options Outstanding Weighted Average Remaining Contractual Life (Years)	7 years 29 days
Options Outstanding Weighted Average Exercise Price	$ 2.26
Options Number Exercisable	1,782,002
Options Exercisable Weighted Average Exercise Price	$ 2.89
Range 1
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 0.94
Range of Exercise Prices, upper limit	$ 1.05
Options Number Outstanding	104,000
Options Outstanding Weighted Average Remaining Contractual Life (Years)	9 years 11 months 12 days
Options Outstanding Weighted Average Exercise Price	$ 1.05
Options Exercisable Weighted Average Exercise Price	$ 0.00
Range 2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 1.06
Range of Exercise Prices, upper limit	$ 1.20
Options Number Outstanding	943,533
Options Outstanding Weighted Average Remaining Contractual Life (Years)	9 years 11 months 1 day
Options Outstanding Weighted Average Exercise Price	$ 1.20
Range 3
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 1.21
Range of Exercise Prices, upper limit	$ 2.40
Options Number Outstanding	746,644
Options Outstanding Weighted Average Remaining Contractual Life (Years)	5 years 11 months 5 days
Options Outstanding Weighted Average Exercise Price	$ 2.17
Options Number Exercisable	527,107
Options Exercisable Weighted Average Exercise Price	$ 2.23
Range 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 2.41
Range of Exercise Prices, upper limit	$ 2.63
Options Number Outstanding	734,712
Options Outstanding Weighted Average Remaining Contractual Life (Years)	7 years 11 months 5 days
Options Outstanding Weighted Average Exercise Price	$ 2.55
Options Number Exercisable	543,343
Options Exercisable Weighted Average Exercise Price	$ 2.60
Range 5
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 2.64
Range of Exercise Prices, upper limit	$ 10.74
Options Number Outstanding	741,058
Options Outstanding Weighted Average Remaining Contractual Life (Years)	3 years 5 months 1 day
Options Outstanding Weighted Average Exercise Price	$ 3.59
Options Number Exercisable	711,552
Options Exercisable Weighted Average Exercise Price	$ 3.61