Other Obligations (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Capital lease obligations
Future payments on capital equipment lease obligation payments
2018	$ 512
2019	1,706
2020	857
2021	27
Total	3,102
Less: interest	115
Total principal payments	2,987
Less: current portion	1,707
Capital equipment lease obligations, net of current portion	1,280
Federal Coal Lease Obligation [Member]
Other Obligations
2019	600
2020	600
2021	600
2022	600
Federal coal Lease obligations	$ 1,800