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Line of Credit (Details) - Line of Credit [Member] - USD ($)
$ in Millions
12 Months Ended
Jan. 07, 2022
Dec. 31, 2021
Dec. 31, 2020
Line of Credit Facility [Line Items]      
Credit facility with a bank   $ 40 $ 40
Line of credit basis points   1.50%  
Line of credit unused portion per year (in percent)   0.25%  
Revolving credit facility, expiration date   Sep. 30, 2021  
Subsequent Event [Member]      
Line of Credit Facility [Line Items]      
Credit facility with a bank $ 40    
Revolving credit facility, expiration date Jan. 07, 2024