Operating 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 expense	$ 1,333	$ 2,663
Short term lease expense	14	29
Variable lease expense	392	810
Sublease income	(7)	(16)
Total lease expense	$ 1,732	$ 3,486