Goodwill and Other Intangible Assets (Schedule of Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets
Gross Carrying Value	$ 83,274	$ 82,980
Accumulated Amortization	(34,976)	(33,144)
Net Carrying Amount	48,298	49,836
Non-compete agreements
Finite-Lived Intangible Assets
Gross Carrying Value	1,386	1,372
Accumulated Amortization	(1,139)	(1,046)
Net Carrying Amount	247	326
Patents
Finite-Lived Intangible Assets
Gross Carrying Value	366	358
Accumulated Amortization	(173)	(165)
Net Carrying Amount	193	193
Customer relationships
Finite-Lived Intangible Assets
Gross Carrying Value	37,337	37,129
Accumulated Amortization	(12,069)	(11,388)
Net Carrying Amount	25,268	25,741
Trademarks and trade names
Finite-Lived Intangible Assets
Gross Carrying Value	8,497	8,481
Accumulated Amortization	(3,657)	(3,416)
Net Carrying Amount	4,840	5,065
Technology
Finite-Lived Intangible Assets
Gross Carrying Value	35,688	35,640
Accumulated Amortization	(17,938)	(17,129)
Net Carrying Amount	$ 17,750	$ 18,511
Weighted Average
Finite-Lived Intangible Assets
Weighted Average Amortization Period In Years	15 years
Weighted Average | Non-compete agreements
Finite-Lived Intangible Assets
Weighted Average Amortization Period In Years	4 years	4 years
Weighted Average | Patents
Finite-Lived Intangible Assets
Weighted Average Amortization Period In Years	10 years	10 years
Weighted Average | Customer relationships
Finite-Lived Intangible Assets
Weighted Average Amortization Period In Years	18 years	18 years
Weighted Average | Trademarks and trade names
Finite-Lived Intangible Assets
Weighted Average Amortization Period In Years	15 years	15 years
Weighted Average | Technology
Finite-Lived Intangible Assets
Weighted Average Amortization Period In Years	14 years	14 years