Leases (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Finance lease obligation	$ 4,852	$ 5,049
Finance lease right-of-use assets	6,534	6,750
Operating lease right-of-use assets	6,235	0
Operating lease, liability	6,252	0
Germany
Lessee, Lease, Description [Line Items]
Finance lease obligation	4,800	5,000
Finance lease right-of-use assets	6,500	6,700
Finance lease, right-of-use asset, amortization	3,600	$ 3,500
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	700		$ 6,200
Operating lease, liability	700		$ 6,200
Scenario, Adjustment
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	6,900
Operating lease, liability	$ 6,900