Summary of Options Outstanding (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding Options, Number Outstanding	6,045,912	6,730,520
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	6 years 7 months 24 days
Options Exercisable, Number Exercisable	3,195,701	3,352,116
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	5 years 1 month 10 days
Exercise Price 1
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 0.20
Outstanding Options, Number Outstanding	1,295
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	6 months 22 days
Options Exercisable, Number Exercisable	1,295
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	6 months 22 days
Exercise Price 2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 0.40
Outstanding Options, Number Outstanding	3,527
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	1 year 26 days
Options Exercisable, Number Exercisable	3,527
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	1 year 26 days
Exercise Price 3
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 0.68
Outstanding Options, Number Outstanding	1,068,735
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	2 years 6 months 22 days
Options Exercisable, Number Exercisable	1,068,735
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	2 years 6 months 22 days
Exercise Price 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 1.00
Outstanding Options, Number Outstanding	431,019
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	4 years 1 month 10 days
Options Exercisable, Number Exercisable	431,019
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	4 years 1 month 10 days
Exercise Price 5
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 2.00
Outstanding Options, Number Outstanding	25,270
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	4 years 11 months 19 days
Options Exercisable, Number Exercisable	25,270
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	4 years 11 months 19 days
Exercise Price 6
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 2.64
Outstanding Options, Number Outstanding	63,777
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	5 years 6 months 22 days
Options Exercisable, Number Exercisable	63,777
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	5 years 6 months 22 days
Exercise Price 7
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 4.48
Outstanding Options, Number Outstanding	1,440,263
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	6 years 6 months 7 days
Options Exercisable, Number Exercisable	1,021,837
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	6 years 4 months 21 days
Exercise Price 8
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 6.84
Outstanding Options, Number Outstanding	1,498,537
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	8 years 1 month 28 days
Options Exercisable, Number Exercisable	331,333
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	8 years 1 month 13 days
Exercise Price 9
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 12.72
Outstanding Options, Number Outstanding	279,452
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	8 years 4 months 21 days
Options Exercisable, Number Exercisable	105,162
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	8 years 4 months 21 days
Exercise Price 10
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 14.12
Outstanding Options, Number Outstanding	532,067
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	8 years 7 months 21 days
Options Exercisable, Number Exercisable	136,871
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	8 years 7 months 21 days
Exercise Price 11
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 20.82
Outstanding Options, Number Outstanding	335,500
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	9 years 3 months 11 days
Options Exercisable, Number Exercisable	6,875
Options Exercisable, Weighted Average Remaining Contractual Life (Years)	9 years 3 months 11 days
Exercise Price 12
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 25.38
Outstanding Options, Number Outstanding	211,470
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	9 years 6 months 15 days
Exercise Price 13
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price	$ 33.19
Outstanding Options, Number Outstanding	155,000
Outstanding Options, Weighted Average Remaining Contractual Life (Years)	9 years 9 months 15 days