LEASES - Maturities of lease liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Lessor, Lease, Description [Line Items]
2022 (excluding the three months ended March 31, 2022)	$ 16,310
Year 1	18,466	$ 20,474
Year 2	16,996	17,941
Year 3	14,156	16,634
Year 4	10,047	13,640
Year 5		9,610
Thereafter	68,363
Thereafter		65,902
Total lease payments	144,338	144,201
Less imputed interest	(42,399)	(42,333)
Total	$ 101,939	$ 101,868
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Lease Liability, Current, Lease Liability, Noncurrent	Lease Liability, Current, Lease Liability, Noncurrent
Finance lease liability
2022 (excluding the three months ended March 31, 2022)	$ 1,092
Year 1	1,463	$ 1,269
Year 2	1,354	1,278
Year 3	1,132	1,169
Year 4	532	975
Year 5		484
Thereafter		3,145
Thereafter	3,145
Total lease payments	8,718	8,320
Less imputed interest	(2,211)	(2,268)
Finance lease liability	$ 6,507	$ 6,052	$ 2,200
Finance Lease, Liability, Statement of Financial Position [Extensible List]	Lease Liability, Current, Lease Liability, Noncurrent	Lease Liability, Current, Lease Liability, Noncurrent
Maturities of future undiscounted lease payments
2022 (excluding the three months ended March 31, 2022)	$ 4,042
2023	4,807
2024	4,406
2025	4,288
2026	3,916
Thereafter	10,455
Total future lease payments	31,914
Network asset
Finance lease liability
Lease income	$ 1,000