Income Taxes (Schedule Of Temporary Differences That Give Rise To Deferred Tax Assets (Liabilities)) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Abstract]
Accrued liabilities	$ 42,151	$ 32,498
Lease liabilities	35,888	32,476
Implicit price concessions	7,031	4,165
Stock compensation expense	4,047	5,425
State net operating loss carryforwards	2,030	2,678
Other	888	592
Deferred income tax assets	92,035	77,834
Amortization of intangible assets	(40,619)	(39,377)
Right of use lease assets	(32,788)	(28,807)
Accelerated tax depreciation	(31,686)	(21,942)
Current assets	(3,921)	(2,510)
Market valuation of investments	(2,382)	(2,058)
State income taxes	(1,161)	(1,477)
Other	(142)	(167)
Deferred income tax liabilities	(112,699)	(96,338)
Net deferred income tax liabilities	$ (20,664)	$ (18,504)