Income Taxes (Schedule Of Deferred Income Tax Assets And Liabilities) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Assets:
Accruals not currently deductible	$ 5,111,242	$ 4,546,767
Stock based compensation	9,586,372	8,594,640
Other	356,039	3,679,680
Total deferred income tax assets	15,053,653	16,821,087
Liabilities:
Excess tax over book depreciation	(39,835,025)	(46,123,681)
Goodwill	(23,341,226)	(18,972,334)
Intangible assets	(5,089,042)	(4,172,726)
Other	(1,309,849)	(6,440,990)
Total deferred income tax liability	(69,575,142)	(75,709,731)
Net deferred income taxes	$ (54,521,489)	$ (58,888,644)