LEASES - Current and Non-current Assets and Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020		Dec. 31, 2019		Mar. 31, 2019	Dec. 31, 2018
Lessor, Lease, Description [Line Items]
Document Period End Date	Jun. 30, 2020
Operating Leases
Operating lease right-of-use-assets, gross	$ 17,026		$ 15,396
Accumulated amortization	(5,086)		(3,714)
Operating lease right-of-use-assets, net	11,940		11,682
Other current liabilities	3,380		3,203
Other non-current liabilities	8,503		8,434
Total operating lease liabilities	11,883		11,637
Finance leases:
Total cost	413,004		424,387
Less: accumulated depreciation	(310,626)		(310,486)
Total net book value	102,378	[1]	113,901	[1]	$ 110,627	$ 117,604
Current portion of long-term debt and other financing arrangements	6,952		6,836
Long-term debt and other financing arrangements	7,671		9,496
Total finance lease liabilities	$ 14,623		$ 16,332
Operating leases	4.80%		4.70%
Finance leases	2.00%		2.10%
Operating Lease, Weighted Average Remaining Lease Term	4 years 9 months 18 days		4 years 10 months 24 days
Finance Lease, Weighted Average Remaining Lease Term	2 years 7 months 6 days		2 years 8 months 12 days
Right-Of-Use Assets Under Finance Lease
Finance leases:
Total cost	$ 33,345		$ 35,875
Less: accumulated depreciation	(16,368)		(15,799)
Total net book value	$ 16,977		$ 20,076

[1] ⁽¹⁾  Reflects property, plant and equipment, net.