Goodwill and Other Intangible Assets (Schedule of Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets
Gross Carrying Value	$ 88,683	$ 88,181
Accumulated Amortization	(32,682)	(30,741)
Net Carrying Amount	56,001	57,440
Non-compete agreements
Finite-Lived Intangible Assets
Gross Carrying Value	4,262	4,238
Accumulated Amortization	(3,339)	(3,100)
Net Carrying Amount	923	1,138
Patents
Finite-Lived Intangible Assets
Gross Carrying Value	379	389
Accumulated Amortization	(164)	(164)
Net Carrying Amount	215	225
Customer relationships
Finite-Lived Intangible Assets
Gross Carrying Value	38,040	37,679
Accumulated Amortization	(9,893)	(9,171)
Net Carrying Amount	28,147	28,508
Trademarks and trade names
Finite-Lived Intangible Assets
Gross Carrying Value	10,114	10,085
Accumulated Amortization	(4,310)	(4,091)
Net Carrying Amount	5,804	5,994
Technology
Finite-Lived Intangible Assets
Gross Carrying Value	35,888	35,790
Accumulated Amortization	(14,976)	(14,215)
Net Carrying Amount	$ 20,912	$ 21,575
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	5 years	5 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	17 years	17 years
Weighted Average | Trademarks and trade names
Finite-Lived Intangible Assets
Weighted Average Amortization Period In Years	14 years	14 years
Weighted Average | Technology
Finite-Lived Intangible Assets
Weighted Average Amortization Period In Years	14 years	14 years