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Basis Of Presentation (Narrative) (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Dec. 31, 2019
Basis Of Accounting [Line Items]        
Total shareholders' equity $ 9,682,882 $ 9,726,176 $ 8,580,944  
Retained Earnings [Member]        
Basis Of Accounting [Line Items]        
Total shareholders' equity $ 10,847,085 10,567,452 $ 10,255,692 $ 10,306,571
Retained Earnings [Member] | Cumulative Effect Period Of Adoption Adjustment [Member] | Accounting Standards Update 2016-13 [Member]        
Basis Of Accounting [Line Items]        
Total shareholders' equity     $ (4,214)