Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Lease cost
Operating lease cost	$ 1,016		$ 2,230
Short-term lease cost	340		561
Variable lease cost	131		284
Total lease cost	$ 1,487		3,075
Lease expense		$ 1,100		$ 2,000
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases			$ 2,702
Weighted-average remaining lease term — operating leases	6 years 10 months 24 days		6 years 10 months 24 days
Weighted-average discount rate — operating leases	4.90%		4.90%