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Stock-based Compensation and Other Employee Benefit Plans Stock Options Activity (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Outstanding Stock Options Activity [Roll Forward]      
Outstanding at December 31 (in shares) 132,670    
Exercisable at December 31 (in shares) 132,670    
Options Outstanding, Weighted Average Exercise Price [Roll Forward]      
Outstanding - weighted average exercise price per share $ 12.10    
Exercised, weighted average exercise price per share 9.60    
Canceled, weighted average exercise price per share 12.19    
Vested and Expected to Vest, weighted average exercise price per share 12.79    
Exercisable, weighted average exercise price per share $ 12.79    
Outstanding, weighted average remaining contractual term 3 years 9 months 18 days 4 years 3 months 18 days  
Vested and Expected to Vest, weighted average remaining contractual term 3 years 9 months 18 days    
Exercisable, weighted average remaining contractual term 3 years 9 months 18 days    
Options outstanding - aggregate intrinsic value $ 6,830,000 $ 5,448,000  
Vested and Expected to Vest, aggregate intrinsic value 6,830,000    
Exercisable, aggregate intrinsic value 6,830,000    
Employee Stock Option [Member]      
Options Outstanding, Weighted Average Exercise Price [Roll Forward]      
Total intrinsic value of options exercised $ 1,500,000 $ 4,700,000 $ 10,900,000
Non Qualified Stock Options [Member]      
Outstanding Stock Options Activity [Roll Forward]      
Outstanding at January 1 (in shares) 169,919    
Exercised (in shares) (36,561)    
Canceled (in shares) (688)    
Outstanding at December 31 (in shares) 132,670 169,919  
Vested and Expected to Vest at December 31(in shares) 132,670    
Exercisable at December 31 (in shares) 132,670