Income Taxes (Schedule Of Deferred Income Tax Assets And Liabilities) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Current
Assets:
Accruals not currently deductible	$ 3,890,858	$ 2,605,711
Stock based compensation	16,636,615	13,508,845
Impairment loss on available-for-sale securities	0	0
Other	3,839,115	4,440,407
Total deferred income tax assets	24,366,588	20,554,963
Liabilities:
Excess tax over book depreciation	0	0
Goodwill	0	0
Unrealized gain on investments	0	0
Intangible assets	0	0
Other	(2,114,430)	(1,117,956)
Net deferred income taxes	22,252,158	19,437,007
Non-Current
Assets:
Accruals not currently deductible	266,802	224,803
Stock based compensation	3,723,490	2,508,304
Impairment loss on available-for-sale securities	73,954	135,724
Other	15,755	19,765
Total deferred income tax assets	4,080,001	2,888,596
Liabilities:
Excess tax over book depreciation	(53,538,861)	(46,017,949)
Goodwill	(16,047,068)	(8,868,168)
Unrealized gain on investments	(961,980)	(6,368,670)
Intangible assets	(3,056,712)	(1,205,230)
Other	0	0
Net deferred income taxes	$ (69,524,620)	$ (59,571,421)