LEASE COST (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Lease Cost Table Line Items
Total lease cost	$ 15,516	$ 15,113
Depreciation and Amortization
Lease Cost Table Line Items
Amortization of ROU assets - finance leases	1,804	1,916
Interest Expense
Lease Cost Table Line Items
Interest on lease liabilities - finance leases	40	56
Cost of Services
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	10,439	12,038
Short-term Lease, Cost	966	997
Variable Lease, Cost	(318)
Selling General And Administrative Expenses
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	606	542
Sublease Income	(228)	(182)
Restructuring
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	240
Impairment
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	1,697
Other income (expense), net
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	310	242
Sublease Income	$ (676)	$ (496)

Lease Cost Table Line Items

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Amount of interest expense on finance lease liability.

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Amount of amortization expense attributable to right-of-use asset from finance lease.

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Amount of lease cost recognized by lessee for lease contract.

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