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Summary of Significant Accounting Policies (Narrative) (Details) - shares
 3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
ASU 2019-12 [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Change in accounting principle, accounting standards update, adopted true   true  
Change in accounting principle, accounting standards update, immaterial effect true   true  
Change in accounting principle, accounting standards update, adoption date Jan. 01, 2021   Jan. 01, 2021  
Stock Options [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Number of potential diluted securities outstanding 521,000 523,000 521,000 523,000
Number of securities included in calculation of diluted earnings per share 267,000 301,000 288,000 303,000
Restricted Stock [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Number of potential diluted securities outstanding 162,000 149,000 162,000 149,000
Number of securities included in calculation of diluted earnings per share 16,000 38,000 44,000 58,000