Leases - Lease Expense for the Operating and Short-term Leases (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases
Operating lease expense	$ 1,294	$ 2,559
Short-term lease expense	165	336
Total lease expense	$ 1,459	$ 2,895