Goodwill and Intangible Assets (Textuals) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Asset impairment charges, patent		$ 2.8
Asset impairment charges, trademark		10.0
Foreign currency translation gains (losses)	$ 0.9	0.3
Amortization expense	2.4	$ 2.6	$ 3.5
Estimated annual amortization expense, 2018	2.2
Estimated annual amortization expense, 2019	2.2
Estimated annual amortization expense, 2020	2.1
Estimated annual amortization expense, 2021	2.1
Estimated annual amortization expense, 2022	$ 2.1