Goodwill and Other Intangible Assets (Schedule Of Components Of Other Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 74,135	$ 73,990
Accumulated Amortization	(54,513)	(53,262)
Total	19,622	20,728
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	53,035	52,890
Accumulated Amortization	(44,600)	(43,617)
Total	$ 8,435	$ 9,273
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	(5,935)	(5,775)
Total	$ 9,465	$ 9,625
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	(3,978)	(3,870)
Total	$ 322	$ 430
Useful Lives (in years)	10 years	10 years
Licensing Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,400	$ 1,400
Total	$ 1,400	$ 1,400