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Long-Term Debt (Details) - Line of Credit - USD ($)
9 Months Ended
Sep. 30, 2017
Nov. 02, 2017
Revolving Credit Facility    
Debt Instrument [Line Items]    
Current borrowing capacity $ 350,000,000  
Remaining borrowing capacity 184,100,000  
Outstanding line of credit $ 165,000,000  
Automatic decrease in borrowing base 25.00%  
Covenant compliance, minimum required current ratio 100.00%  
Covenant compliance, maximum allowable leverage ratio 400.00%  
Letter of Credit    
Debt Instrument [Line Items]    
Maximum borrowing capacity $ 15,000,000.0  
Letters of credit outstanding $ 900,000  
Subsequent Event | Revolving Credit Facility    
Debt Instrument [Line Items]    
Current borrowing capacity   $ 575,000,000