Annual report pursuant to Section 13 and 15(d)

Stock Incentive Plan - Stock Options Activity (Details)

v3.8.0.1
Stock Incentive Plan - Stock Options Activity (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Number of Options      
Beginning balance (in shares) 3,971,382 4,139,440 3,893,573
Granted (in shares) 390,353 665,000 747,100
Exercised (in shares) (401,031) (320,892) (332,600)
Forfeited (in shares) (41,500) (194,562) (168,633)
Expired (in shares) (85,557) (317,604)  
Ending balance (in shares) 3,833,647 3,971,382 4,139,440
Options exercisable (in shares) 2,494,009    
Options expected to vest (in shares) 1,339,638    
Weighted-Average Exercise Price      
Beginning balance (in usd per share) $ 7.300 $ 7.740 $ 7.721
Granted (in usd per share) 6.061 4.703 6.404
Exercised (in usd per share) 4.935 3.286 3.467
Forfeited (in usd per share) 6.421 8.154 9.409
Expired (in usd per share) 10.157 11.293  
Ending balance (in usd per share) 7.367 $ 7.300 $ 7.740
Options exercisable (in usd per share) 8.280    
Expected to vest (in usd per share) $ 5.667    
Outstanding, remaining contractual term 5 years 2 months 19 days    
Exercisable, remaining contractual term 3 years 7 months 2 days    
Expected to vest, remaining contractual term 8 years 3 months    
Outstanding, aggregate intrinsic value $ 7,691    
Exercisable, aggregate intrinsic value 3,741    
Expected to vest, aggregate intrinsic value $ 3,950