Significant Accounting Policies (Narrative) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Property, Plant and Equipment [Line Items]
Number of operating leases		460
Number of finance leases		105
Intra-entity foreign currency transactions, long-term investments | $		$ 18,129	$ 1,967	$ 19,636
Number of stock option compensation plans		3
Mascus International Holdings BV [Member] | ASU 2016-15 [Member]
Property, Plant and Equipment [Line Items]
Reclassification of contingent consideration | $	$ 1,302
Liability Classified Awards [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Award vesting period		5 years