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Long-term Debt - Additional Information (Details)
$ in Millions
3 Months Ended 12 Months Ended
Oct. 12, 2016
Mar. 31, 2019
USD ($)
Lender
Mar. 31, 2018
USD ($)
Mar. 26, 2018
Mar. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Long-term debt            
Number of lender holding percentage of outstanding amount | Lender   1        
Percentage of outstanding principal amount held by lender   1.00%        
Interest Expense            
Long-term debt            
Refinancing charges     $ 2.3      
Minimum            
Long-term debt            
Threshold percentage comparing present value of remaining cash flows   10.00%        
Term Loan B-1            
Long-term debt            
Due date of loan Sep. 25, 2021          
Variable interest rate base   LIBOR        
Term Loan B-1 | LIBOR            
Long-term debt            
Interest rate added to base rate (as a percent)       2.75%    
Interest rate, variable interest rate floor (as a percent)       0.75%    
2023 Term Loans            
Long-term debt            
Due date of loan         Mar. 26, 2023  
Variable interest rate base   LIBOR        
2023 Term Loans | Level 2            
Long-term debt            
Amount to be realized in the future   $ 277.5     $ 277.5 $ 274.7
2023 Term Loans | LIBOR            
Long-term debt            
Interest rate added to base rate (as a percent)         2.25%  
Interest rate, variable interest rate floor (as a percent)         0.00%