Additional Information Regarding Options Outstanding (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares	1,030,795
Range One
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 0.50
Number of Shares	37,240
Weighted- Average Remaining Contractual Life (in Years)	2 years 3 months 11 days
Range Two
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 0.53
Number of Shares	45,625
Weighted- Average Remaining Contractual Life (in Years)	4 years 7 days
Range Three
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 0.89
Number of Shares	15,723
Weighted- Average Remaining Contractual Life (in Years)	4 years 6 months 15 days
Range Four
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 1.03
Number of Shares	182,754
Weighted- Average Remaining Contractual Life (in Years)	5 years 3 months 22 days
Range Five
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 1.21
Number of Shares	177,387
Weighted- Average Remaining Contractual Life (in Years)	6 years 1 month 17 days
Range Six
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 1.46
Number of Shares	128,020
Weighted- Average Remaining Contractual Life (in Years)	7 years 9 months
Range Seven
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 2.17
Number of Shares	66,394
Weighted- Average Remaining Contractual Life (in Years)	9 years 2 months 9 days
Range Eight
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 4.74
Number of Shares	349,574
Weighted- Average Remaining Contractual Life (in Years)	9 years 6 months 29 days
Range Nine
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 11.36
Number of Shares	28,078
Weighted- Average Remaining Contractual Life (in Years)	9 years 9 months 22 days