Debt - Narrative (Details) - USD ($)
3 Months Ended 12 Months Ended
May 24, 2018
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Nov. 10, 2015
Debt Instrument [Line Items]                          
Term loan   $ 147,750,000               $ 147,750,000      
Interest expense   2,974,000 $ 2,979,000 $ 3,071,000 $ 3,061,000 $ 3,028,000 $ 2,972,000 $ 5,560,000 $ 3,419,000 $ 12,085,000 $ 14,979,000 $ 13,528,000  
Secured Debt | 2018 Term Loan                          
Debt Instrument [Line Items]                          
Debt instrument face amount $ 150,000,000                        
Debt instrument term (years) 5 years                        
Frequency of periodic payment                   Quarterly      
Periodic payment of principal                   $ 400,000      
Interest expense                   11,200,000      
Unamortized issuance cost and original issue discount   2,000,000.0       $ 2,500,000       $ 2,000,000.0 $ 2,500,000    
Debt instrument covenant, maximum debt-to-total capitalization ratio                   35.00%      
Secured Debt | 2018 Term Loan | LIBOR                          
Debt Instrument [Line Items]                          
Variable rate floor (percent)                     1.00%    
Basis spread on variable rate (percent)                     4.75%    
Interest rate during period (percent)                   6.55%      
Senior Secured Debt | 2015 Term Loan                          
Debt Instrument [Line Items]                          
Debt instrument face amount                         $ 150,000,000
Revolving Credit Facility | 2018 Revolving Credit Facility                          
Debt Instrument [Line Items]                          
Debt instrument term (years) 3 years                        
Credit facility borrowing capacity $ 85,000,000                        
Borrowings outstanding   0               $ 0      
Debt instrument covenant, maximum debt-to-total capitalization ratio                   35.00%      
Commitment fee (percent)                   0.40%      
Commitment fees in interest expense                   $ 400,000      
Deferred debt issuance costs $ 1,500,000                        
Amortization of deferred issuance costs                   500,000      
Remaining deferred issuance costs, net of accumulated amortization   $ 700,000               $ 700,000      
Revolving Credit Facility | 2018 Revolving Credit Facility | Minimum                          
Debt Instrument [Line Items]                          
Commitment fee (percent) 0.30%                        
Revolving Credit Facility | 2018 Revolving Credit Facility | Maximum                          
Debt Instrument [Line Items]                          
Commitment fee (percent) 0.60%                        
Revolving Credit Facility | 2018 Revolving Credit Facility | Base Rate                          
Debt Instrument [Line Items]                          
Variable rate floor (percent) 1.00%                        
Revolving Credit Facility | 2018 Revolving Credit Facility | Base Rate | Minimum                          
Debt Instrument [Line Items]                          
Basis spread on variable rate (percent) 1.00%                        
Revolving Credit Facility | 2018 Revolving Credit Facility | Base Rate | Maximum                          
Debt Instrument [Line Items]                          
Basis spread on variable rate (percent) 2.50%                        
Revolving Credit Facility | 2018 Revolving Credit Facility | Eurodollar                          
Debt Instrument [Line Items]                          
Variable rate floor (percent) 0.00%                        
Revolving Credit Facility | 2018 Revolving Credit Facility | Eurodollar | Minimum                          
Debt Instrument [Line Items]                          
Basis spread on variable rate (percent) 2.00%                        
Revolving Credit Facility | 2018 Revolving Credit Facility | Eurodollar | Maximum                          
Debt Instrument [Line Items]                          
Basis spread on variable rate (percent) 3.50%