Leases - Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease cost	$ 3,055	$ 5,022
Short-term lease costs	137	286
Variable lease costs	592	1,009
Total lease costs	$ 3,784	$ 6,317