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Share-Based Compensation - Summary of Stock Options Outstanding (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Number of shares vested and exercisable 557,311 410,236 448,371
Options vested and exercisable weighted average remaining contractual life 5 years 4 months 6 days 5 years 5 months 1 day 5 years 26 days
Options vested and exercisable weighted average exercise price $ 16.82 $ 10.57 $ 7.54
Options vested and exercisable intrinsic value $ 11,080 $ 9,224 $ 7,029
$4.54 - 22.76      
Range of exercise prices, lower range $ 4.54    
Range of exercise prices, upper range $ 22.76    
Number of shares vested and exercisable 424,130    
Options vested and exercisable weighted average remaining contractual life 4 years 4 months 10 days    
Options vested and exercisable weighted average exercise price $ 12.41    
Options vested and exercisable intrinsic value $ 10,303    
$23.57 - 32.85      
Range of exercise prices, lower range $ 23.57    
Range of exercise prices, upper range $ 32.85    
Number of shares vested and exercisable 107,456    
Options vested and exercisable weighted average remaining contractual life 8 years 3 months 22 days    
Options vested and exercisable weighted average exercise price $ 30.10    
Options vested and exercisable intrinsic value $ 709    
$32.90 - 37.30      
Range of exercise prices, lower range $ 32.90    
Range of exercise prices, upper range $ 37.30    
Number of shares vested and exercisable 25,725    
Options vested and exercisable weighted average remaining contractual life 9 years 2 months 9 days    
Options vested and exercisable weighted average exercise price $ 34.07    
Options vested and exercisable intrinsic value $ 68    
$4.54 - 20.92      
Range of exercise prices, lower range   $ 4.54  
Range of exercise prices, upper range   $ 20.92  
Number of shares vested and exercisable   338,308  
Options vested and exercisable weighted average remaining contractual life   4 years 9 months  
Options vested and exercisable weighted average exercise price   $ 8.03  
Options vested and exercisable intrinsic value   $ 8,465  
$20.96 - 26.50      
Range of exercise prices, lower range   $ 20.96  
Range of exercise prices, upper range   $ 26.50  
Number of shares vested and exercisable   71,928  
Options vested and exercisable weighted average remaining contractual life   8 years 6 months 22 days  
Options vested and exercisable weighted average exercise price   $ 22.50  
Options vested and exercisable intrinsic value   $ 759  
$4.31 - 8.65      
Range of exercise prices, lower range     $ 4.31
Range of exercise prices, upper range     $ 8.65
Number of shares vested and exercisable     421,237
Options vested and exercisable weighted average remaining contractual life     4 years 10 months 21 days
Options vested and exercisable weighted average exercise price     $ 7.04
Options vested and exercisable intrinsic value     $ 6,814
$8.70 - 22.76      
Range of exercise prices, lower range     $ 8.70
Range of exercise prices, upper range     $ 22.76
Number of shares vested and exercisable     27,134
Options vested and exercisable weighted average remaining contractual life     7 years 9 months 26 days
Options vested and exercisable weighted average exercise price     $ 15.31
Options vested and exercisable intrinsic value     $ 215