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Summary of Significant Accounting Policies (Narrative) (Details) - shares
 3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
ASU 2019-12 [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Change in accounting principle, accounting standards update, adopted true  
Change in accounting principle, accounting standards update, immaterial effect true  
Change in accounting principle, accounting standards update, adoption date Jan. 01, 2021  
Stock Options [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Number of potential diluted securities outstanding 503,000 585,000
Number of securities included in calculation of diluted earnings per share 311,000 311,000
Restricted Stock [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Number of potential diluted securities outstanding 168,000 77,000
Number of securities included in calculation of diluted earnings per share 64,000 84,000