LEASES - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finance Leases
2021	$ 13,894
2022	13,894
2023	24,711
2024	15,256
2025	4,187
Thereafter	75
Total lease payments	72,017
Less: Imputed interest	(5,880)
Total lease obligations	66,137	$ 89,176
Less: Current obligations	(11,655)	(30,779)
Long-term finance lease obligations	54,482	58,397
Operating Leases
2021	7,004
2022	6,456
2023	6,192
2024	5,918
2025	5,049
Thereafter	1,321
Total lease payments	31,940
Less: Imputed interest	(3,412)
Total operating lease liabilities	28,528	11,862
Less: Current obligations	(6,838)	(6,050)
Long-term operating lease obligations	$ 21,690	$ 5,812