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Income Taxes (Provision for Income Taxes) (Narrative) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Taxes      
Revaluation of deferred tax liability, benefit $ 0 $ 0 $ (1,262)
Investment tax credit amount 170,500 $ 8,500 $ 19,400
State and local jurisdiction [Member]      
Income Taxes      
Tax credit carryforwards available for state tax purposes, net of federal impact $ 1,400    
Tax credit carryforwards available for state tax purposes, expiration year 2024