Impairment Charges (Details Textual) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Impairments	$ 5.4	$ 0.1

Amount after tax of (gain) loss recognized for the (reversal of write-down) write-down to fair value, less cost to sell, of a discontinued operation.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration