Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation and Summary of Significant Accounting Policies - Fair Value, by Balance Sheet (Details)

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Basis of Presentation and Summary of Significant Accounting Policies - Fair Value, by Balance Sheet (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Jun. 30, 2018
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Feb. 28, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Carrying Amount $ 754,544   $ 754,544   $ 660,200  
Fair Value 721,899   721,899   617,333  
Borrowings on revolving credit facility     31,600 $ 78,115    
Stated interest rate           2.75%
Amount outstanding 687,439   687,439   619,064  
Paid-in-Kind interest converted to principal     8,450 $ 0    
Term loan facility            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Carrying Amount 481,250   481,250   490,625  
Fair Value 494,484   494,484   486,945  
Revolving Credit Facility            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Carrying Amount 29,015   29,015   78,000  
Fair Value 29,015   29,015   78,000  
Convertible senior notes            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Carrying Amount 82,500   82,500   82,500  
Fair Value $ 61,215   $ 61,215   43,313  
Stated interest rate 2.75%   2.75%     2.75%
Equity component of convertible debt $ 13,000   $ 13,000     $ 13,000
Amount outstanding 82,500   82,500      
Other debt            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Carrying Amount 3,329   3,329   9,075  
Fair Value 3,329   3,329   9,075  
Second Lien Credit Agreement            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Carrying Amount 158,450   158,450   0  
Fair Value 133,856   133,856   0  
Paid-in-Kind interest converted to principal 8,500          
Second Lien Credit Agreement | Penny Warrants            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Equity component of convertible debt 14,900   14,900      
Second Lien Credit Agreement | Market Warrants            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Equity component of convertible debt 9,300   $ 9,300      
Unamortized Debt Issuance Costs [Member]            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Carrying Amount         $ 41,100  
Revolving Credit Facility            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Repayments of debt   $ 78,000        
Borrowings on revolving credit facility $ 29,000          
Revolving Credit Facility | Line of Credit            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Repayments of debt   $ 78,000