Annual report pursuant to Section 13 and 15(d)

Equity Compensation - Summary of Weighted Average Exercise Prices and Contractual Lives for Outstanding and Exercisable Stock Options (Details)

v3.10.0.1
Equity Compensation - Summary of Weighted Average Exercise Prices and Contractual Lives for Outstanding and Exercisable Stock Options (Details) - Stock Option - $ / shares
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Outstanding        
Shares (in shares) 1,327,919 1,506,604 1,539,017 1,661,700
Weighted average remaining life (in years) 4 years 7 months 6 days      
Weighted average exercise price (in usd per share) $ 18.13 $ 14.65 $ 12.91 $ 10.96
Exercisable        
Shares (in shares) 1,043,596 1,252,315 1,255,295  
Weighted average remaining life (in years) 3 years 6 months      
Weighted average exercise price (in usd per share) $ 14.27 $ 11.17 $ 9.59  
$2.67 - $3.19        
Share-based Compensation Arrangement by Share-based Payment Award        
Exercise price, lower range (in usd per share) 2.67      
Exercise price, upper range (in usd per share) $ 3.19      
Outstanding        
Shares (in shares) 309,199      
Weighted average remaining life (in years) 10 months 24 days      
Weighted average exercise price (in usd per share) $ 2.86      
Exercisable        
Shares (in shares) 309,199      
Weighted average remaining life (in years) 10 months 24 days      
Weighted average exercise price (in usd per share) $ 2.86      
$7.68 - $13.63        
Share-based Compensation Arrangement by Share-based Payment Award        
Exercise price, lower range (in usd per share) 7.68      
Exercise price, upper range (in usd per share) $ 13.63      
Outstanding        
Shares (in shares) 410,646      
Weighted average remaining life (in years) 3 years      
Weighted average exercise price (in usd per share) $ 10.04      
Exercisable        
Shares (in shares) 410,646      
Weighted average remaining life (in years) 3 years      
Weighted average exercise price (in usd per share) $ 10.04      
$22.69 - $35.82        
Share-based Compensation Arrangement by Share-based Payment Award        
Exercise price, lower range (in usd per share) 22.69      
Exercise price, upper range (in usd per share) $ 35.82      
Outstanding        
Shares (in shares) 589,821      
Weighted average remaining life (in years) 7 years 7 months 6 days      
Weighted average exercise price (in usd per share) $ 30.90      
Exercisable        
Shares (in shares) 305,498      
Weighted average remaining life (in years) 6 years 7 months 6 days      
Weighted average exercise price (in usd per share) $ 29.59      
$45.89 - $45.89        
Share-based Compensation Arrangement by Share-based Payment Award        
Exercise price, lower range (in usd per share) 45.89      
Exercise price, upper range (in usd per share) $ 45.89      
Outstanding        
Shares (in shares) 18,253      
Weighted average remaining life (in years) 6 years 2 months 12 days      
Weighted average exercise price (in usd per share) $ 45.89      
Exercisable        
Shares (in shares) 18,253      
Weighted average remaining life (in years) 6 years 2 months 12 days      
Weighted average exercise price (in usd per share) $ 45.89