Debt (Details) - USD ($)
$ in Thousands
3 Months Ended 8 Months Ended 9 Months Ended
May 03, 2018
Mar. 13, 2018
Feb. 12, 2018
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Debt                  
Debt Issuance cost expensed       $ 373 $ 909   $ 1,337 $ 2,766  
Dividends paid             694 121,129  
Loss on debt extinguishment         $ 330   6,058 $ 330  
Revolving Credit Facility                  
Debt                  
Amount of revolving credit facility $ 100,000   $ 50,000            
Debt Term     5 years            
Interest Expense and Other Financing Costs                  
Debt                  
Write-off of unamortized debt discount and debt issuance costs     $ 4,200            
Write-off of unamortized debt discount     1,900            
Loss on debt extinguishment     6,100            
Credit Agreement                  
Debt                  
Amount of revolving credit facility 100,000   50,000            
Arranger and legal costs expensed     3,700            
Debt Issuance cost capitalized $ 400   1,800            
Repayments of debt     499,700            
Credit Agreement | Revolving Credit Facility                  
Debt                  
Original issue discount     $ 300            
Maximum first lien leverage ratio (as a percent)     35.00%            
Credit Agreement | General and Administrative Expense.                  
Debt                  
Debt Issuance cost expensed     $ 1,900            
Term Loans                  
Debt                  
Principal amount     360,000            
Net proceeds from issuance of debt     355,900            
Cash on hand for term loan repayment     $ 800            
Debt Term     7 years            
Original issue discount     $ 900 $ 3,664   $ 3,664 $ 3,664   $ 5,083
Amortization rate (as a percent)     1.00%            
Effective interest rate (as a percent)       5.14%   5.14% 5.14%    
Effective yield             5.81%    
Repayments of debt       $ 20,000   $ 80,000      
Term Loans | London Interbank Offered Rate (LIBOR)                  
Debt                  
Base Spread     2.75%            
Minimum | Term Loans                  
Debt                  
Mandatory prepayments, annual excess cash flows, effective December 31, 2019 (as a percent)     0.00%            
Maximum | Term Loans                  
Debt                  
Mandatory prepayments, annual excess cash flows, effective December 31, 2019 (as a percent)     50.00%            
IPO                  
Debt                  
Proceeds received from issuance of shares   $ 156,500              
Class A | IPO                  
Debt                  
Proceeds received from issuance of shares     $ 143,000