Leases - Lease Cost (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Lease cost
Total operating lease cost	$ 1,226
Depreciation of leased assets	333
Interest on lease liabilities	1,230
Total finance lease cost	1,563
Total lease cost	2,789
Short-term lease and variable lease costs	200
Service
Lease cost
Total operating lease cost	597
Research & development
Lease cost
Total operating lease cost	66
Selling
Lease cost
Total operating lease cost	355
General & administrative
Lease cost
Total operating lease cost	$ 208