Options Outstanding (Detail) (USD $)	6 Months Ended
	Jun. 30, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding Number of Options	1,592,160
Options Outstanding WA Remaining Contractual Term	7 years 10 months 10 days
Options Exercisable Number of Options	911,184
Options Exercisable WA Remaining Contractual Term	6 years 9 months 1 day
Exercise Price 1
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	1.32
Options Outstanding Number of Options	30,000
Options Outstanding WA Remaining Contractual Term	9 years 5 months 15 days
Options Exercisable WA Remaining Contractual Term	0 years
Exercise Price 2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	1.35
Options Outstanding Number of Options	188,691
Options Outstanding WA Remaining Contractual Term	6 years 11 months 16 days
Options Exercisable Number of Options	185,823
Options Exercisable WA Remaining Contractual Term	6 years 11 months 16 days
Exercise Price 3
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	1.65
Options Outstanding Number of Options	50,000
Options Outstanding WA Remaining Contractual Term	9 years 10 months 29 days
Options Exercisable Number of Options	1,042
Options Exercisable WA Remaining Contractual Term	9 years 10 months 29 days
Exercise Price 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	1.66
Options Outstanding Number of Options	74,750
Options Outstanding WA Remaining Contractual Term	9 years 3 months 13 days
Options Exercisable WA Remaining Contractual Term	0 years
Exercise Price 5
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	1.67
Options Outstanding Number of Options	229,000
Options Outstanding WA Remaining Contractual Term	9 years 5 months 8 days
Options Exercisable WA Remaining Contractual Term	0 years
Exercise Price 6
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	1.86
Options Outstanding Number of Options	110,000
Options Outstanding WA Remaining Contractual Term	9 years 8 months 26 days
Options Exercisable WA Remaining Contractual Term	0 years
Exercise Price 7
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	2.06
Options Outstanding Number of Options	110,000
Options Outstanding WA Remaining Contractual Term	9 years 8 months 25 days
Options Exercisable Number of Options	6,876
Options Exercisable WA Remaining Contractual Term	9 years 8 months 25 days
Exercise Price 8
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	2.21
Options Outstanding Number of Options	100,000
Options Outstanding WA Remaining Contractual Term	7 years 10 months 4 days
Options Exercisable Number of Options	75,000
Options Exercisable WA Remaining Contractual Term	7 years 10 months 4 days
Exercise Price 9
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	2.25
Options Outstanding Number of Options	112,500
Options Outstanding WA Remaining Contractual Term	8 years 9 months 12 days
Options Exercisable Number of Options	112,500
Options Exercisable WA Remaining Contractual Term	8 years 9 months 12 days
Exercise Price 10
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	2.35
Options Outstanding Number of Options	80,500
Options Outstanding WA Remaining Contractual Term	8 years 5 months 5 days
Options Exercisable Number of Options	80,500
Options Exercisable WA Remaining Contractual Term	8 years 5 months 5 days
Exercise Price 11
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	2.71
Options Outstanding Number of Options	106,875
Options Outstanding WA Remaining Contractual Term	8 years 13 days
Options Exercisable Number of Options	57,096
Options Exercisable WA Remaining Contractual Term	8 years 13 days
Exercise Price 12
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	3.05
Options Outstanding Number of Options	66,000
Options Outstanding WA Remaining Contractual Term	6 years 2 months 18 days
Options Exercisable Number of Options	58,503
Options Exercisable WA Remaining Contractual Term	6 years 2 months 18 days
Exercise Price 13
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	3.15
Options Outstanding Number of Options	33,066
Options Outstanding WA Remaining Contractual Term	5 years 11 months 17 days
Options Exercisable Number of Options	33,066
Options Exercisable WA Remaining Contractual Term	5 years 11 months 17 days
Exercise Price 14
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	3.24
Options Outstanding Number of Options	11,500
Options Outstanding WA Remaining Contractual Term	5 years 10 months 15 days
Options Exercisable Number of Options	11,500
Options Exercisable WA Remaining Contractual Term	5 years 10 months 15 days
Exercise Price 15
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	3.80
Options Outstanding Number of Options	11,500
Options Outstanding WA Remaining Contractual Term	5 years 9 months 4 days
Options Exercisable Number of Options	11,500
Options Exercisable WA Remaining Contractual Term	5 years 9 months 4 days
Exercise Price 16
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	4.29
Options Outstanding Number of Options	11,500
Options Outstanding WA Remaining Contractual Term	5 years 1 month 24 days
Options Exercisable Number of Options	11,500
Options Exercisable WA Remaining Contractual Term	5 years 1 month 24 days
Exercise Price 17
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	7.00
Options Outstanding Number of Options	266,278
Options Outstanding WA Remaining Contractual Term	4 years 11 months 8 days
Options Exercisable Number of Options	266,278
Options Exercisable WA Remaining Contractual Term	4 years 11 months 8 days