Annual report pursuant to Section 13 and 15(d)

Line of Credit (Details)

v3.6.0.2
Line of Credit (Details)
Dec. 16, 2016
USD ($)
Dec. 31, 2016
USD ($)
Dec. 15, 2016
USD ($)
Line of Credit Facility [Line Items]      
Revolving credit facility $ 40,000,000   $ 80,000,000
Financial covenants, minimum net worth   $ 255,000,000.0  
Financial covenants, percent of net income added to net worth requirement   50.00%  
Financial covenants, percent of proceeds from stock issuance added to net worth requirement   100.00%  
Financial covenants, maximum impairment of certain assets deducted from net worth requirement   $ 30,000,000.0  
Financial covenants, maximum EBITDA ratio   2.5  
Financial covenants, minimum interest coverage ratio   2.0  
Borrowings under credit agreement   $ 0  
Outstanding letters of credit   7,700,000  
Revolving Credit Facility      
Line of Credit Facility [Line Items]      
Available borrowings for general corporate purposes     $ 20,000,000.0
Fees on unused borrowings 0.50%    
Revolving Credit Facility | London Interbank Offered Rate (LIBOR)      
Line of Credit Facility [Line Items]      
Basis spread on variable interest rate 2.00%    
Letter of Credit      
Line of Credit Facility [Line Items]      
Fees on unused borrowings 2.00%    
Revolving credit facility, unused portion   $ 32,300,000