LEASES - Schedule of future maturities of lease liabilities (Details) $ in Thousands	Sep. 30, 2019 USD ($)
Finance
Remainder of 2019	$ 3,406
2020	20,222
2021	6,565
2022	154
2023	133
Thereafter	24
Total minimum lease payments	30,504
Less amount representing interest	1,339
Present value of minimum lease payments	29,165
Operating
Remainder of 2019	8,746
2020	24,067
2021	23,134
2022	13,341
2023	6,504
Thereafter	22,073
Total minimum lease payments	97,865
Less amount representing interest	15,664
Present value of minimum lease payments	82,201
Mining equipment
Finance
Remainder of 2019	925
2020	3,699
2021	2,157
2022	0
2023	0
Thereafter	0
Total minimum lease payments	6,781
Operating
Remainder of 2019	311
2020	627
2021	0
2022	0
2023	0
Thereafter	0
Total minimum lease payments	$ 938