Leases - Lease Costs (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Leases [Abstract]
Operating lease cost	$ 1,347	$ 2,727
Short-term lease cost	2,232	4,169
Short-term lease cost - related party	920	1,822
Total lease cost	4,499	$ 8,718
Cash paid for amounts included in the measurement of lease liabilities - operating leases	$ 1,375
Weighted-average remaining lease term - operating leases	5 years 10 months 28 days	5 years 10 months 28 days
Weighted-average discount rate - operating leases	5.50%	5.50%