Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Lease cost
Operating lease cost	$ 1,214
Short-term lease cost	221
Variable lease cost	153
Total lease cost	1,588
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 1,307
Weighted-average remaining lease term — operating leases	6 years 10 months 24 days
Weighted-average discount rate — operating leases	4.70%
Lease expense		$ 900