LEASES AND RELATED PARTY LEASES - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
ROU assets	$ 87,600	$ 83,635
Current lease liabilities	13,526	12,818
Non-current lease liabilities	94,840	88,118
Total lease liabilities	$ 108,366	$ 100,936
Leased facilities
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term (in years)	11 years	11 years 7 months 6 days
Weighted average discount rate	5.00%	4.60%
Leased vehicles
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term (in years)	2 years 2 months 12 days	2 years 3 months 18 days
Weighted average discount rate	2.50%	2.30%