Annual report pursuant to Section 13 and 15(d)

Options Outstanding and Exercisable (Detail)

v3.8.0.1
Options Outstanding and Exercisable (Detail) - 2002 Stock Incentive Plan
shares in Thousands
 12 Months Ended
Dec. 31, 2017
$ / shares
shares
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Options Outstanding Number of Shares | shares 6,737
Options Outstanding Weighted Average Exercise Price $ 1.80
Options Outstanding Weighted Average Remaining Life (Years) 7 years 2 months 15 days
Options Exercisable Number of Shares | shares 3,454
Options Exercisable Weighted Average Exercise Price $ 2.24
Range One  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices, Lower Limit 0.43
Range of Exercise Prices, Upper Limit $ 1.21
Options Outstanding Number of Shares | shares 1,428
Options Outstanding Weighted Average Exercise Price $ 0.80
Options Outstanding Weighted Average Remaining Life (Years) 8 years 7 months 24 days
Options Exercisable Number of Shares | shares 451
Options Exercisable Weighted Average Exercise Price $ 0.97
Range Two  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices, Lower Limit 1.22
Range of Exercise Prices, Upper Limit $ 1.44
Options Outstanding Number of Shares | shares 917
Options Outstanding Weighted Average Exercise Price $ 1.42
Options Outstanding Weighted Average Remaining Life (Years) 7 years 8 months 1 day
Options Exercisable Number of Shares | shares 563
Options Exercisable Weighted Average Exercise Price $ 1.42
Range Three  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices, Lower Limit 1.45
Range of Exercise Prices, Upper Limit $ 1.60
Options Outstanding Number of Shares | shares 1,481
Options Outstanding Weighted Average Exercise Price $ 1.48
Options Outstanding Weighted Average Remaining Life (Years) 8 years 11 months 4 days
Options Exercisable Number of Shares | shares 3
Options Exercisable Weighted Average Exercise Price $ 1.45
Range Four  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices, Lower Limit 1.61
Range of Exercise Prices, Upper Limit $ 2.38
Options Outstanding Number of Shares | shares 1,573
Options Outstanding Weighted Average Exercise Price $ 2.02
Options Outstanding Weighted Average Remaining Life (Years) 6 years 8 months 12 days
Options Exercisable Number of Shares | shares 1,207
Options Exercisable Weighted Average Exercise Price $ 2.08
Range Five  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices, Lower Limit 2.39
Range of Exercise Prices, Upper Limit $ 5.07
Options Outstanding Number of Shares | shares 1,338
Options Outstanding Weighted Average Exercise Price $ 3.20
Options Outstanding Weighted Average Remaining Life (Years) 4 years 21 days
Options Exercisable Number of Shares | shares 1,230
Options Exercisable Weighted Average Exercise Price $ 3.25