Equity And Stock-Based Compensation (Schedule Of Stock Options Outstanding) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity And Stock-Based Compensation [Line Items]
Weighted Average Exercise Price of Options Outstanding, Granted	$ 13.30	$ 8.56	$ 6.19
Weighted average remaining years of contractual life	2 years 10 months 21 days	2 years 4 months 24 days	4 years 8 months 12 days
Weighted average remaining years of contractual life	2 years 1 month 21 days	3 years 7 months 17 days	3 years 1 month 10 days
Aggregate Intrinsic Value, Exercised	$ 327,170	$ 374,022	$ 133,000
Aggregate Intrinsic Value, Ending balance	$ 2,188,011	$ 4,197,000	$ 938,503
Class A [Member]
Equity And Stock-Based Compensation [Line Items]
Common Stock Options Outstanding, Beginning balance	568,250	709,850	672,350
Common Stock Options Outstanding, Granted	112,000	80,000	175,000
Common Stock Options Outstanding, Exercised	(185,685)	(157,600)	(137,500)
Common Stock Options Outstanding, Expired	(8,000)	(64,000)
Common Stock Options Outstanding, Ending balance	486,565	568,250	709,850
Weighted Average Exercise Price of Options Outstanding, Beginning price	$ 6.88	$ 6.66	$ 6.24
Weighted Average Exercise Price of Options Outstanding, Granted	13.30	8.56	6.19
Weighted Average Exercise Price of Options Outstanding, Exercised	6.09	6.21	4.00
Weighted Average Exercise Price of Options Outstanding, Expired	6.23	6.83
Weighted Average Exercise Price of Options Outstanding, Ending price	$ 8.68	$ 6.88	$ 6.66
Class B [Member]
Equity And Stock-Based Compensation [Line Items]
Common Stock Options Outstanding, Beginning balance	185,100	185,100	185,100
Common Stock Options Outstanding, Granted
Common Stock Options Outstanding, Exercised	(185,100)
Common Stock Options Outstanding, Ending balance		185,100	185,100
Weighted Average Exercise Price of Options Outstanding, Beginning price	$ 9.90	$ 9.90	$ 9.90
Weighted Average Exercise Price of Options Outstanding, Exercised	$ 9.90
Weighted Average Exercise Price of Options Outstanding, Ending price		$ 9.90	$ 9.90