Income Taxes (Schedule Of Temporary Differences That Give Rise To Deferred Tax Assets (Liabilities)) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Abstract]
Accrued liabilities	$ 32,498	$ 30,702
Lease liabilities	32,476
Stock compensation expense	5,425	5,894
Implicit price concessions	4,165	1,171
State net operating loss carryforwards	2,678	2,422
Other	894	626
Deferred income tax assets	78,136	40,815
Amortization of intangible assets	(39,679)	(38,346)
Right of use lease assets	(28,807)
Accelerated tax depreciation	(21,942)	(19,685)
Current assets	(2,510)	(1,861)
Market valuation of investments	(2,058)	(1,068)
State income taxes	(1,477)	(1,261)
Other	(167)	(192)
Deferred income tax liabilities	(96,640)	(62,413)
Net deferred income tax liabilities	$ (18,504)	$ (21,598)