Annual report pursuant to Section 13 and 15(d)

Indebtedness (Details)

v3.20.4
Indebtedness (Details)
 12 Months Ended
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Apr. 16, 2020
USD ($)
Sep. 29, 2017
USD ($)
numberOfSegments
Line of Credit Facility [Line Items]          
Proceeds from senior credit facility $ 65,000,000 $ 20,000,000 $ 7,000,000    
Revolving Credit Facility [Member]          
Line of Credit Facility [Line Items]          
Proceeds from senior credit facility 112,500,000 67,500,000      
Utilized for outstanding letters of credit 18,326,000 13,970,000      
Line of Credit Facility, Current Borrowing Capacity       $ 225,000,000  
Available borrowing capacity $ 94,174,000 $ 68,530,000     $ 150,000,000
Line of Credit Facility, Interest Rate at Period End 3.25% 3.20%      
Credit facility term (in years) | numberOfSegments         5
Senior credit facility amount       250,000,000  
Additional borrowing capacity of credit facility       $ 25,000,000  
Base reference rate of credit facilities LIBOR        
Basis spread on variable rate minimum (in hundredths)       2.25% 1.25%
Basis spread on variable rate maximum (in hundredths)       2.75% 1.75%
Debt Instrument, Basis Spread on Variable Rate 1.00%        
Line of credit facility, interest rate, minimum $ 0.0300        
Debt instrument, basis spread on alternative variable rate, minimum 0.0025        
Debt instrument, basis spread on alternative variable rate, maximum $ 0.0075        
Letter of Credit [Member]          
Line of Credit Facility [Line Items]          
Sublimit on revolving credit facility         $ 30,000,000
Swing line loan [Member]          
Line of Credit Facility [Line Items]          
Sublimit on revolving credit facility         $ 30,000,000
Federal funds [Member]          
Line of Credit Facility [Line Items]          
Debt Instrument, Basis Spread on Variable Rate 0.50%