v3.20.4
Long-Term Debt - Summary of Debt (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Jun. 10, 2016
Debt Instrument [Line Items]        
Unamortized discount and debt issuance costs $ (11,058) $ (14,834)    
Total long-term debt 633,942 632,406    
Current portion of long-term debt 2,240 0    
Total long-term debt, including current portion 636,182 632,406    
Amortization of deferred financing costs and original issue discount 4,049 3,666 $ 3,333  
Level 2        
Debt Instrument [Line Items]        
Estimated fair value of total long-term debt outstanding 645,700 673,800    
Senior Notes        
Debt Instrument [Line Items]        
Amortization of deferred financing costs and original issue discount 3,800 3,400 $ 3,100  
Senior Notes | 9.25% Senior Secured Notes due June 2023        
Debt Instrument [Line Items]        
Total long-term debt, net of current portion, before debt issuance costs and discount $ 645,000 645,000    
Debt instrument, percentage rate 9.25%     9.25%
Unamortized debt discount $ 16,100      
Debt issuance costs 9,400      
Senior Notes | 6.50% Senior Notes due April 2021, net of current portion        
Debt Instrument [Line Items]        
Total long-term debt, net of current portion, before debt issuance costs and discount 0 $ 2,240    
Current portion of long-term debt $ 2,200      
Debt instrument, percentage rate 6.50%