Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lease cost
Total operating lease cost	$ 1,207	$ 2,433
Depreciation of leased assets	332	665
Interest on lease liabilities	1,311	2,541
Total finance lease cost	1,643	3,206
Total lease cost	2,850	5,639
Short-term lease and variable lease costs	200	400
Service
Lease cost
Total operating lease cost	583	1,180
Research and development
Lease cost
Total operating lease cost	86	152
Sales and marketing
Lease cost
Total operating lease cost	345	699
General & administrative
Lease cost
Total operating lease cost	$ 193	$ 402