Goodwill and Other Intangible Assets (Schedule Of Components Of Other Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 75,962	$ 75,962
Accumulated Amortization	(64,907)	(64,640)
Net Carrying Amount	11,055	11,322
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	54,862	54,862
Accumulated Amortization	(52,747)	(52,640)
Net Carrying Amount	$ 2,115	$ 2,222
Useful Lives (in years)	11 years	11 years
Trade names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 15,400	$ 15,400
Accumulated Amortization	(7,860)	(7,700)
Net Carrying Amount	$ 7,540	$ 7,700
Useful Lives (in years)	24 years	24 years
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 4,300	$ 4,300
Accumulated Amortization	(4,300)	(4,300)
Net Carrying Amount	$ 0	$ 0
Useful Lives (in years)	10 years	10 years
Licensing Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,400	$ 1,400
Net Carrying Amount	$ 1,400	$ 1,400