Leases - Lease Expense for the Operating and Short-term Leases (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases
Operating lease expense	$ 819	$ 3,378
Short-term lease expense	86	422
Total lease expense	$ 905	$ 3,800