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	$ 3,773	$ 7,477
Finance lease expense:
Amortization of assets	245	489
Interest on lease liabilities	13	28
Short-term lease expense	98	134
Variable lease expense	802	1,420
Total lease expense	$ 4,931	$ 9,548