Income Taxes (Summary Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Net operating loss carryforwards	$ 5,623	$ 17,897
Tax credit carryforwards	5,078	5,516
Deferred revenue, accruals and reserves	66,926	70,539
Other	2,379	7,401
Total deferred tax assets	80,006	101,353
Valuation allowance	(5,613)	(6,598)
Net deferred tax assets	74,393	94,755
Property and equipment	(4,167)	(3,466)
Other	(2,394)	(3,608)
Deferred Tax Liabilities, Gross	(6,561)	(7,074)
Total deferred tax assets	$ 67,832	$ 87,681