Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Finance lease expense:
Amortization of right-of-use assets	$ 16	$ 49
Interest on lease liabilities	0	1
Operating lease expense	1,605	3,249
Short-term lease expense	244	468
Variable lease expense	18	54
Total lease expense	$ 1,883	$ 3,821