Income Taxes (Schedule Of Components Of Income Tax Expense By Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Abstract]
Statutory income tax expense	$ 56,730	$ 27,844	$ 26,991
State income tax expense, net of federal income tax expense	11,153	5,483	4,847
Executive compensation	4,566	4,123	2,760
Excess tax benefits upon vesting of share based payment awards	(108)	(252)	(1,276)
Remeasurement of deferred tax assets			1,548
Federal energy credits	(8,549)	(17,256)	(2,426)
State tax credits	(900)
Other	1,191	(301)	(369)
Income tax expense	$ 64,083	$ 19,641	$ 32,075