Schedule of Significant Option Groups Outstanding (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares	3,841
Options Exercisable, Shares	2,004
Options Outstanding, Weighted-Average Exercise Price	$ 4.64
Options Exercisable, Weighted-Average Exercise Price	$ 3.70
Range One
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	6 years 3 months 22 days
Options Outstanding, Shares	864
Options Exercisable, Shares	492
Range Of Exercise Prices, Lower Limit	$ 0.47
Range Of Exercise Prices, Upper Limit	$ 2.58
Options Outstanding, Weighted-Average Exercise Price	$ 1.69
Options Exercisable, Weighted-Average Exercise Price	$ 1.60
Range Two
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	6 years 9 months 4 days
Options Outstanding, Shares	1,278
Options Exercisable, Shares	661
Range Of Exercise Prices, Lower Limit	$ 2.67
Range Of Exercise Prices, Upper Limit	$ 2.74
Options Outstanding, Weighted-Average Exercise Price	$ 2.69
Options Exercisable, Weighted-Average Exercise Price	$ 2.70
Range Three
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	3 years 10 months 17 days
Options Outstanding, Shares	795
Options Exercisable, Shares	490
Range Of Exercise Prices, Lower Limit	$ 3.23
Range Of Exercise Prices, Upper Limit	$ 4.81
Options Outstanding, Weighted-Average Exercise Price	$ 4.29
Options Exercisable, Weighted-Average Exercise Price	$ 4.14
Range Four
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5 years 3 months 4 days
Options Outstanding, Shares	904
Options Exercisable, Shares	361
Range Of Exercise Prices, Lower Limit	$ 5.80
Range Of Exercise Prices, Upper Limit	$ 16.95
Options Outstanding, Weighted-Average Exercise Price	$ 10.54
Options Exercisable, Weighted-Average Exercise Price	$ 7.76