Leases and Right of Use Assets - Supplemental Balance Sheet Information (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Operating leases:
Operating leases - right of use assets	$ 15,433
Current maturities of operating leases	8,423
Non-current operating leases	7,010
Total operating lease liabilities	15,433
Finance leases:
Property, plant and equipment, at cost	80,307
Accumulated amortization	(18,250)
Property, plant and equipment, net	62,057
Current maturities of finance leases	17,574
Long-term debt and finance leases	54,396
Total lease obligations	$ 71,970
Weighted average remaining lease term (in months):
Operating leases	22 months
Finance leases	36 months
Weighted average discount rate:
Operating leases	4.13%
Finance leases	2.46%