LEASES - Schedule of Lease Costs and Other Lease Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Lease cost:
Amortization of right-of-use assets	$ 593	$ 1,505
Interest expense	213	555
Fixed lease cost	4,308	12,851
Short-term lease cost	853	2,261
Variable lease cost	329	712
Total lease cost	6,296	17,884
Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows for finance leases	666	1,870
Operating cash flows for operating leases	2,963	9,837
Right-of-use assets obtained in exchange for new finance lease liabilities	0	6,857
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 831	$ 1,419
Weighted-average remaining lease term - finance leases (years)	6 years 8 months 12 days	6 years 8 months 12 days
Weighted-average remaining lease term - operating leases (years)	12 years	12 years
Weighted-average discount rate - finance leases	5.20%	5.20%	5.20%
Weighted-average discount rate - operating leases	5.20%	5.20%
Vehicles, equipment and property
Lease cost:
Fixed lease cost	$ 2,351	$ 7,271
Landfill
Lease cost:
Fixed lease cost	$ 1,957	$ 5,580