Adoption of ASU No. 2016-02, Leases (Lease Costs) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 828	$ 1,675
Variable lease cost	478	849
Short-term lease cost	1,071	3,686
Total lease cost	2,377	6,210
Lease operating expense
Lessee, Lease, Description [Line Items]
Total lease cost	1,029	3,675
General and administrative
Lessee, Lease, Description [Line Items]
Total lease cost	$ 1,348	$ 2,535