Stock-Based Compensation And Stock Repurchases (Schedule Of Stock Options Outstanding And Exercisable) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Equity And Stock-Based Compensation [Line Items]
Number of Stock Options, Granted		219,408
Weighted Average Exercise Price of Options Outstanding, Granted		$ 16.12	$ 16.40
Class A [Member]
Equity And Stock-Based Compensation [Line Items]
Number of Stock Options, Beginning balance		586,469	524,589	524,589
Number of Stock Options, Granted		219,408		126,840
Number of Stock Options, Exercised		(69,500)		(60,000)
Number of Stock Options, Forfeited		(25,000)		(4,960)
Number of Stock Options Outstanding, Ending balance	711,377	711,377		586,469	524,589
Weighted Average Exercise Price of Options Outstanding, Beginning price		$ 14.01	$ 12.50	$ 12.50
Weighted Average Exercise Price of Options Outstanding, Granted		16.12		16.40
Weighted Average Exercise Price of Options Outstanding, Exercised		13.42		6.02
Weighted Average Exercise Price of Options Outstanding, Forfeited		13.42		12.08
Weighted Average Exercise Price of Options Outstanding, Ending price	$ 14.74	$ 14.74		$ 14.01	$ 12.50
Weighted Average Remaining Years of Contractual Life		3 years 15 days		2 years 10 months 17 days	3 years 1 month 24 days
Aggregate Intrinsic Value, Beginning balance		$ 1,530,528	$ 3,054,325	$ 3,054,325
Aggregate Intrinsic Value, Exercised	$ 185,175	185,175		610,249
Aggregate Intrinsic Value, Ending balance	$ 164,930	$ 164,930		$ 1,530,528	$ 3,054,325