Summary Of Significant Accounting Policies (Schedule Of Other Operating Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other operating income	$ 75,095	$ (9,132)	$ (1,300)
CARES Act Grant Income [Member]
Other operating income	80,225
Lost Revenue [Member] | CARES Act Grant Income [Member]
Other operating income	44,784
Incremental PTO [Member] | CARES Act Grant Income [Member]
Other operating income	21,425
Hard Costs [Member] | CARES Act Grant Income [Member]
Other operating income	$ 14,016