LEASE COST (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lease Cost Table Line Items
Total lease cost	$ 13,442	$ 15,609	$ 42,930	$ 45,767
Depreciation and Amortization
Lease Cost Table Line Items
Amortization of ROU assets - finance leases	1,617	1,933	5,131	5,777
Interest Expense
Lease Cost Table Line Items
Interest on lease liabilities - finance leases	32	49	108	157
Cost of Services
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	9,511	11,446	30,051	35,126
Short-term Lease, Cost	1,186	1,029	3,153	2,909
Variable Lease, Cost	306	(1)	943	(285)
Selling General And Administrative Expenses [Member]
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	730	530	2,057	1,493
Sublease Income	(183)	(220)	(625)	(614)
Restructuring
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	428	261	1,069	697
Impairment
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	141	948	2,061	1,456
Other income (expense), net
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	310	310	930	839
Sublease Income	$ (636)	$ (676)	$ (1,948)	$ (1,788)

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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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