LEASES - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Operating leases:
Operating leases - right of use assets	$ 7,866	$ 11,775
Current operating lease obligations	3,028	6,050
Long-term operating lease obligations	4,966	5,812
Total operating lease liabilities	7,994	11,862
Finance leases:
Property and equipment, at cost	385,174	372,885
Accumulated amortization	(142,414)	(124,216)
Property and equipment, net	242,760	248,669
Current finance lease obligations	25,928	30,779
Long-term finance lease obligations	60,363	58,397
Total lease obligations	$ 86,291	$ 89,176
Weighted average remaining lease term:
Operating leases	52 months	45 months
Finance leases	42 months	44 months
Weighted average discount rate:
Operating leases	4.00%	4.03%
Finance leases	3.50%	3.34%
Equipment finance leases
Finance leases:
Property and equipment, at cost	$ 121,889	$ 120,236
Accumulated amortization	(35,990)	(30,990)
Property and equipment, net	$ 85,899	$ 89,246