Operations and Summary of Significant Accounting Policies - Intangible Assets Indefinite-lived Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Indefinite-Lived Intangible Assets
Amortization of Intangible Assets	$ 6,200	$ 6,000	$ 6,100
Finite-Lived Intangible Assets, Gross	54,537	51,442
Finite-Lived Intangible Assets, Accumulated Amortization	(25,211)	(28,578)
Intangible Assets, Net (Excluding Goodwill)	29,326	22,864
North America
Indefinite-Lived Intangible Assets
Finite-Lived Intangible Assets, Gross	30,775	23,562
Finite-Lived Intangible Assets, Accumulated Amortization	(13,732)	(13,811)
Intangible Assets, Net (Excluding Goodwill)	17,043	9,751
Europe
Indefinite-Lived Intangible Assets
Finite-Lived Intangible Assets, Gross	23,762	27,880
Finite-Lived Intangible Assets, Accumulated Amortization	(11,479)	(14,767)
Intangible Assets, Net (Excluding Goodwill)	12,283	13,113
Customer Relationships
Indefinite-Lived Intangible Assets
Reclassifications	(626)	46
Amortization of Intangible Assets	1,574	1,793
Finite-Lived Intangible Assets, Gross	17,678	21,217	21,242
Finite-Lived Intangible Assets, Accumulated Amortization	(10,869)	(14,945)	(13,152)
Intangible Assets, Net (Excluding Goodwill)	6,809	6,272	8,090
Patents
Indefinite-Lived Intangible Assets
Reclassifications		212
Amortization of Intangible Assets	187	149
Finite-Lived Intangible Assets, Gross	2,350	1,718	1,513
Finite-Lived Intangible Assets, Accumulated Amortization	(545)	(528)	(379)
Intangible Assets, Net (Excluding Goodwill)	1,805	1,190	1,134
Noncompete Agreements Trademarks and Other
Indefinite-Lived Intangible Assets
Reclassifications		119
Amortization of Intangible Assets	2,495	2,040
Finite-Lived Intangible Assets, Gross	12,225	6,727	10,578
Finite-Lived Intangible Assets, Accumulated Amortization	(2,817)	(4,100)	(7,203)
Intangible Assets, Net (Excluding Goodwill)	9,408	2,627	3,375
Unpatented Technology
Indefinite-Lived Intangible Assets
Reclassifications		1,512
Amortization of Intangible Assets	1,976	2,058
Finite-Lived Intangible Assets, Gross	21,667	21,162	21,604
Finite-Lived Intangible Assets, Accumulated Amortization	(10,979)	(9,003)	(8,656)
Intangible Assets, Net (Excluding Goodwill)	10,688	$ 12,159	$ 12,948
Trade Name
Indefinite-Lived Intangible Assets
Intangible Assets, Net (Excluding Goodwill)	$ 600

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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