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Line of Credit (Details)
$ in Millions
12 Months Ended
Dec. 31, 2020
USD ($)
Jan. 29, 2021
USD ($)
Dec. 31, 2019
USD ($)
Debt Instrument [Line Items]      
Borrowings under the line of credit agreement $ 0.0   $ 0.0
Letters of credit outstanding amount 6.1    
Available borrowing under letter of credit $ 43.9    
Maximum ratio of total liabilities to tangible net worth 2.50    
Company's leverage ratio 0.0000    
Line of Credit      
Debt Instrument [Line Items]      
Increase in the total line of credit $ 100.0    
Line of Credit | Unsecured Revolving Line of Credit      
Debt Instrument [Line Items]      
Total availability under line of credit agreement 50.0    
Line of Credit | Letter of Credit      
Debt Instrument [Line Items]      
Total availability under line of credit agreement $ 10.0    
Line of Credit | Letter of Credit | Subsequent Event      
Debt Instrument [Line Items]      
Total availability under line of credit agreement   $ 20.0  
Minimum | Line of Credit | London Interbank Offered Rate (LIBOR)      
Debt Instrument [Line Items]      
Debt instrument basis spread on variable rate (as a percentage) 1.00%    
Maximum | Line of Credit | London Interbank Offered Rate (LIBOR)      
Debt Instrument [Line Items]      
Debt instrument basis spread on variable rate (as a percentage) 1.50%