LEASE COST (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Lease Cost Table Line Items
Total lease cost	$ 13,972	$ 14,538	$ 29,488	$ 29,651
Depreciation and Amortization
Lease Cost Table Line Items
Amortization of ROU assets - finance leases	1,710	1,928	3,514	3,844
Interest Expense
Lease Cost Table Line Items
Interest on lease liabilities - finance leases	36	52	76	108
Cost of Services
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	10,101	11,642	20,540	23,680
Short-term Lease, Cost	1,001	883	1,967	1,880
Variable Lease, Cost	319	(284)	637	(284)
Selling General And Administrative Expenses
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	721	858	1,327	1,400
Sublease Income	(214)	(212)	(442)	(394)
Restructuring
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	401		641
Impairment
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	223		1,920
Other income (expense), net
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	310	287	620	529
Sublease Income	$ (636)	$ (616)	$ (1,312)	$ (1,112)

Lease Cost Table Line Items

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Amount of variable lease cost net.

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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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Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

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