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Long-Term Debt (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Aug. 31, 2018
Nov. 01, 2016
Dec. 31, 2014
Nov. 11, 2013
Debt Instrument [Line Items]            
Line of Credit Facility, Maximum Borrowing Capacity     $ 100,000,000.0 $ 175,000,000.0   $ 250,000,000.0
Allowable Amount for Issuance of Letters of Credit $ 30,000,000.0       $ 20,000,000.0  
Debt Instrument, Covenant, Leverage Ratio 2          
Debt Covenant, Minimum Net Income Requirement $ 1.00          
Debt Instrument, Covenant minimum tangible net worth 250,000,000.0          
Long-term Line of Credit 0 $ 0        
Letters of Credit Outstanding on a Line of Credit, Amount Outstanding 11,300,000 10,700,000        
Line of Credit Facility, Remaining Borrowing Capacity $ 88,700,000 $ 89,300,000        
Prime Rate [Member]            
Debt Instrument [Line Items]            
Debt Instrument, Basis Spread on Variable Rate 0.00%          
Accordion Feature [Member]            
Debt Instrument [Line Items]            
Line of Credit Facility, Maximum Borrowing Capacity $ 100,000,000.0          
Maximum [Member]            
Debt Instrument [Line Items]            
Line of Credit Facility, Commitment Fee Percentage 0.175%          
Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member]            
Debt Instrument [Line Items]            
Debt Instrument, Basis Spread on Variable Rate 0.90%          
Minimum [Member]            
Debt Instrument [Line Items]            
Line of Credit Facility, Commitment Fee Percentage 0.0725%          
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member]            
Debt Instrument [Line Items]            
Debt Instrument, Basis Spread on Variable Rate 0.70%