LEASES - Weighted average remaining lease terms and discount rates (Details)	Mar. 31, 2021	Dec. 31, 2020
LEASES
Operating leases, weighted average remaining lease term	5 years 9 months 18 days	5 years 10 months 24 days
Financing leases, weighted average remaining lease term	10 years 7 months 6 days	10 years 10 months 24 days
Operating leases, weighted average discount rate	4.90%	5.00%
Financing leases, weighted average discount rate	4.20%	3.30%