Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Finance lease cost
Amortization of leased assets	$ 1,189	$ 1,050
Interest on lease liabilities	2,372	2,511
Operating lease cost	883	1,230
Total leased cost	$ 4,444	$ 4,791
Weighted-average remaining lease term (in years)
Finance leases	9 years 6 months 26 days		9 years 9 months 26 days
Operating leases	4 years 10 months 21 days
Weighted-average discount rate
Finance leases	11.05%		11.05%
Operating leases	5.06%