v3.3.1.900
Share Compensation and Pension Plans - Summary of Option Activity (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Number of Share Options, Outstanding [Roll Forward]        
Outstanding, start of period (in shares) 2,362,975 2,439,413 2,795,437  
Granted (in shares) 24,000 45,000 49,000  
Exercised (in shares) (456,776) (120,596) (289,614)  
Expired (in shares) (3,442)   (691)  
Forfeited (in shares) (558) (842) (114,719)  
Outstanding, end of period (in shares) 1,926,199 2,362,975 2,439,413 2,795,437
Total options exercisable outstanding, Number of Share Options (in shares) 1,874,855      
Weighted Average Exercise Price [Roll Forward]        
Outstanding, beginning of period (in dollars per share) $ 6.95 $ 6.76 $ 6.70  
Granted (in dollars per share) 13.98 12.01 10.61  
Exercised (in dollars per share) 7.27 4.91 6.13  
Expired (in dollars per share) 8.61   7.67  
Forfeited (in dollars per share) 9.00 7.74 8.51  
Outstanding, end of period (in dollars per share) 6.96 6.95 6.76 $ 6.70
Total options exercisable outstanding, Weighted Average Exercise Price (in dollars per share) 6.82      
Weighted Average Grant-Date Fair Value (in dollars per share) $ 3.31 $ 4.28 $ 2.80  
Outstanding, Weighted Average Remaining Contractual Term 4 years 1 month 24 days 4 years 10 months 10 days 5 years 9 months 6 years 9 months
Total options exercisable outstanding, Weighted Average Remaining Contractual Term 3 years 11 months 27 days      
Options Outstanding, Aggregate Intrinsic Value $ 15,306 $ 13,791 $ 10,174 $ 7,271
Options Exercised, Aggregate Intrinsic Value 3,521 $ 930 $ 1,397  
Total options exercisable outstanding, Aggregate Intrinsic Value $ 15,171      
Minimum        
Weighted Average Exercise Price [Roll Forward]        
Outstanding, beginning of period (in dollars per share) $ 3.28 $ 3.28 $ 3.28  
Granted (in dollars per share)   11.38 9.99  
Outstanding, end of period (in dollars per share) 3.28 3.28 3.28 $ 3.28
Total options exercisable outstanding, Weighted Average Exercise Price (in dollars per share) 3.28      
Maximum        
Weighted Average Exercise Price [Roll Forward]        
Outstanding, beginning of period (in dollars per share) 12.42 11.22 10.00  
Granted (in dollars per share) 13.98 12.42 11.22  
Outstanding, end of period (in dollars per share) 13.98 $ 12.42 $ 11.22 $ 10.00
Total options exercisable outstanding, Weighted Average Exercise Price (in dollars per share) $ 12.42