Stockholders' Equity (Deficiency) - Options Outstanding Separated into Range of Exercise Price (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding	3,428,258	3,233,235
Options outstanding, Weighted average remaining contractual life	5 years 8 months 23 days
Options outstanding, Weighted average exercise price	$ 6.264	$ 4.033
Options exercisable	2,581,849
Options exercisable, Weighted average remaining contractual life	4 years 7 months 7 days
Options exercisable, Weighted average exercise price	$ 1.582
$0.070-0.901 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise price, Lower limit	$ 0.070
Range of exercise price, Upper limit	$ 0.901
Options outstanding	758,047
Options outstanding, Weighted average remaining contractual life	3 years 1 month 13 days
Options outstanding, Weighted average exercise price	$ 0.744
Options exercisable	758,047
Options exercisable, Weighted average remaining contractual life	3 years 1 month 13 days
Options exercisable, Weighted average exercise price	$ 0.744
$1.039-1.576 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise price, Lower limit	$ 1.039
Range of exercise price, Upper limit	$ 1.576
Options outstanding	1,672,067
Options outstanding, Weighted average remaining contractual life	4 years 11 months 15 days
Options outstanding, Weighted average exercise price	$ 1.260
Options exercisable	1,657,236
Options exercisable, Weighted average remaining contractual life	4 years 11 months 11 days
Options exercisable, Weighted average exercise price	$ 1.257
$6.230-8.800 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise price, Lower limit	$ 6.230
Range of exercise price, Upper limit	$ 8.800
Options outstanding	182,773
Options outstanding, Weighted average remaining contractual life	7 years 7 months 16 days
Options outstanding, Weighted average exercise price	$ 6.709
Options exercisable	112,294
Options exercisable, Weighted average remaining contractual life	7 years 6 months 16 days
Options exercisable, Weighted average exercise price	$ 6.775
$12.470 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise price, Upper limit	$ 12.470
Options outstanding	439,971
Options outstanding, Weighted average remaining contractual life	8 years 11 months 4 days
Options outstanding, Weighted average exercise price	$ 12.470
Options exercisable	54,272
Options exercisable, Weighted average remaining contractual life	8 years 8 months 15 days
Options exercisable, Weighted average exercise price	$ 12.470
$21.14-24.23 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise price, Lower limit	$ 21.140
Range of exercise price, Upper limit	$ 24.230
Options outstanding	160,750
Options outstanding, Weighted average remaining contractual life	9 years 5 months 9 days
Options outstanding, Weighted average exercise price	$ 21.991
Options exercisable
Options exercisable, Weighted average remaining contractual life
Options exercisable, Weighted average exercise price
$39.86 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise price, Upper limit	$ 39.860
Options outstanding	214,650
Options outstanding, Weighted average remaining contractual life	9 years 11 months 23 days
Options outstanding, Weighted average exercise price	$ 39.860
Options exercisable
Options exercisable, Weighted average remaining contractual life
Options exercisable, Weighted average exercise price