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Stock-based Compensation - Employee Stock Purchase Plan (Details) - USD ($)
12 Months Ended
May 09, 2018
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Aggregate number of shares of common stock issued or transferred under the incentive stock awards plan (in shares)   1,441,744  
Options outstanding, weighted average exercise price (in dollars per share)   $ 30.42 $ 25.56
Employee Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
ESPP purchase price of common stock, percent of market price, on first and last day of trading date 85.00%    
Fixed contribution rate 10.00%    
Maximum contribution amount $ 25,000    
Compensation cost for ESPP   $ 200,000  
Number of shares issued under the ESPP   25,239  
Aggregate number of shares of common stock issued or transferred under the incentive stock awards plan (in shares)   174,761  
Options outstanding, weighted average exercise price (in dollars per share)   $ 35.74