Equity Awards - Stock Option Plan Activity (Detail) (Service and performance-based employee and director stock options, USD $)
In Thousands, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Service and performance-based employee and director stock options
      
Options Outstanding      
Options outstanding, beginning balance 4,433,706 3,885,193 1,781,499
Options granted 2,072,108 564,442 2,193,701
Options forfeited   (15,929) (90,007)
Options exercised (41,828)    
Options outstanding, ending balance 6,463,986 4,433,706 3,885,193
Weighted Average Exercise Price      
Average exercise price, beginning of period $ 2.38 $ 2.53 $ 3.90
Average exercise price, options granted $ 2.98 $ 1.29 $ 1.46
Average exercise price, forfeited   $ 1.53 $ 3.48
Average exercise price, exercised $ 2.51    
Average exercise price, end of period $ 2.57 $ 2.38 $ 2.53
Weighted Average Grant Date Fair Value      
Average grant date fair value, beginning of period $ 1.63 $ 1.73 $ 2.59
Average grant date fair value, options granted $ 2.34 $ 0.93 $ 1.07
Average grant date fair value, forfeited   $ 1.09 $ 2.52
Average grant date fair value, exercised $ 1.73    
Average grant date fair value, end of period $ 1.86 $ 1.63 $ 1.73
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]      
Average remaining contractual life, options outstanding 4 years 7 months 14 days    
Options exercisable, ending balance 3,297,814    
Average exercise price, options exercisable $ 2.70    
Average remaining contractual life, options exercisable 3 years 3 months 1 day    
Aggregate intrinsic value, options exercisable $ 3,571    
Options expected to vest 3,166,172    
Average exercise price, options expected to vest $ 2.43    
Aggregate intrinsic value, options expected to vest $ 3,158