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Cash Equivalents And Restricted Cash And Securities (Narrative) (Details) - USD ($)
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Restricted Cash and Cash Equivalents Items [Line Items]      
Restricted securities   $ 546,000  
Gross realized gains or losses on cash equivalents $ 0 0 $ 0
Money Market Funds [Member]      
Restricted Cash and Cash Equivalents Items [Line Items]      
Restricted securities   546,000  
Maturity Date Within Three Months [Member] | Money Market Funds [Member]      
Restricted Cash and Cash Equivalents Items [Line Items]      
Restricted securities   $ 546,000  
Maximum [Member] | Maturity Date Within Three Months [Member] | Money Market Funds [Member] | Measurement Input, Expected Term [Member]      
Restricted Cash and Cash Equivalents Items [Line Items]      
Restricted securities maturity period   3 months