Goodwill and Other Intangible Assets (Summary Of Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 799,468	$ 639,157
Finite-Lived Intangible Assets, Accumulated Amortization	(240,461)	(201,815)
Finite-Lived Intangible Assets, Net	559,007	437,342
Indefinite-Lived Trademarks	19,900	19,900
Intangible Assets, Gross (Excluding Goodwill)	819,368	659,057
Total intangible assets	578,907	457,242
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	620,771	527,713
Finite-Lived Intangible Assets, Accumulated Amortization	(198,500)	(167,911)
Finite-Lived Intangible Assets, Net	$ 422,271	359,802
Customer Relationships [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	6 years
Customer Relationships [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	25 years
Advertiser Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 46,282	46,282
Finite-Lived Intangible Assets, Accumulated Amortization	(17,613)	(13,405)
Finite-Lived Intangible Assets, Net	$ 28,669	32,877
Finite-Lived Intangible Asset, Useful Life	11 years
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 118,772	53,761
Finite-Lived Intangible Assets, Accumulated Amortization	(17,971)	(14,420)
Finite-Lived Intangible Assets, Net	$ 100,801	39,341
Trade Names [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Trade Names [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	20 years
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 13,643	11,401
Finite-Lived Intangible Assets, Accumulated Amortization	(6,377)	(6,079)
Finite-Lived Intangible Assets, Net	$ 7,266	$ 5,322
Other Intangible Assets [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Other Intangible Assets [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years