Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Finance lease cost
Amortization of leased assets	$ 1,189	$ 1,050	$ 3,567	$ 3,149
Interest on lease liabilities	2,372	2,512	7,116	7,534
Operating lease cost	542	1,229	2,308	3,689
Total leased cost	$ 4,103	$ 4,791	$ 12,991	$ 14,372
Weighted-average remaining lease term (in years)
Finance leases	9 years 29 days		9 years 29 days		9 years 9 months 26 days
Operating leases	5 years 8 months 19 days		5 years 8 months 19 days
Weighted-average discount rate
Finance leases	11.05%		11.05%		11.05%
Operating leases	4.94%		4.94%