XML 64 R53.htm IDEA: XBRL DOCUMENT v3.10.0.1
Revolving Credit Facility (Details)
6 Months Ended
Jun. 30, 2018
USD ($)
Jul. 26, 2018
USD ($)
Dec. 31, 2017
USD ($)
Line of Credit Facility [Line Items]      
Actual net worth for compliance $ 238,400,000    
Minimum net worth required for compliance $ 125,000,000.0    
Ratio of total liability to net worth 0.34    
Maximum ratio of total liability to net worth for compliance 2    
Borrowings outstanding under revolving credit facility $ 0   $ 0
Fees associated with unused portion of committed amount 0    
Subsequent Event      
Line of Credit Facility [Line Items]      
Actual net worth for compliance   $ 175,000,000  
Revolving Credit Facility      
Line of Credit Facility [Line Items]      
Credit facility maximum borrowings 30,000,000.0    
Standby letter of credit 800,000.0    
Borrowings available under the revolving credit facility $ 29,200,000.0    
Frequency of periodic payment monthly    
Revolving Credit Facility | LIBOR      
Line of Credit Facility [Line Items]      
Stated percentage 2.50%    
Revolving Credit Facility | LIBOR | Subsequent Event      
Line of Credit Facility [Line Items]      
Stated percentage   2.00%