Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease cost	$ 4,244	$ 8,224
Amortization of right-of-use assets	452	904
Interest on lease liabilities	671	1,360
Total finance lease cost	$ 1,123	$ 2,264