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Certain Financial Statement Caption Information - Additional information (Details) - USD ($)
6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Schedule Of Available For Sale Securities [Line Items]    
Other than temporary impairment loss investments available for sale securities $ 0 $ 0
Realized gain on investments $ 0 $ 13,000
Minimum    
Schedule Of Available For Sale Securities [Line Items]    
Available for sale Securities debt maturities period 1 year  
Maximum    
Schedule Of Available For Sale Securities [Line Items]    
Available for sale Securities debt maturities period 2 years