Cash Equivalents And Restricted Cash And Securities (Summary Of Cash Equivalents And Restricted Securities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash Equivalents, Cost Basis	$ 55,010	$ 61,958	$ 34,294	$ 42,236
Cost Basis	10,015	12,030
Restricted Securities, Cost Basis		546
Unrealized Holding Gains
Estimated Market Value	10,015	12,030
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash Equivalents, Cost Basis	10,015	11,484
Restricted Securities, Cost Basis		546
Unrealized Holding Gains
Cash Equivalents, Estimated Market Value	$ 10,015	11,484
Restricted Securities, Estimated Market Value		$ 546