Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease cost	$ 1,877	$ 3,447
Amortization of right-of-use assets	80	160
Interest on lease liabilities	15	30
Total finance lease cost	95	190
Short-term lease cost	1,773	3,764
Total lease expense	$ 3,745	$ 7,401