LEASES - Weighted average remaining lease terms and discount rates (Details)	Sep. 30, 2021	Dec. 31, 2020
LEASES
Operating leases, weighted average remaining lease term	11 years 6 months	5 years 10 months 24 days
Financing leases, weighted average remaining lease term	10 years 6 months	10 years 10 months 24 days
Operating leases, weighted average discount rate	5.40%	5.00%
Financing leases, weighted average discount rate	7.10%	3.30%