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Summary of Significant Accounting Policies (Narrative) (Details) - shares
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 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 526,000 579,000 526,000 579,000
Number of securities included in calculation of diluted earnings per share 286,000 296,000 298,000 304,000
Restricted Stock [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Number of potential diluted securities outstanding 172,000 72,000 172,000 72,000
Number of securities included in calculation of diluted earnings per share 20,000 37,000 49,000 63,000