LEASE COST (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lease Cost Table Line Items
Total lease cost	$ 14,538	$ 16,707	$ 29,651	$ 31,032
Depreciation and Amortization
Lease Cost Table Line Items
Amortization of ROU assets - finance leases	1,928	1,798	3,844	3,405
Interest Expense
Lease Cost Table Line Items
Interest on lease liabilities - finance leases	52	32	108	40
Cost of Services
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	11,642	12,647	23,680	23,346
Short-term Lease, Cost	883	1,247	1,880	2,312
Variable Lease, Cost	(284)		(284)
Selling General And Administrative Expenses
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	858	1,363	1,400	2,630
Sublease Income	(212)	(126)	(394)	(193)
Other income (expense), net
Lease Cost Table Line Items
Operating lease cost (cost resulting from lease payments)	287	242	529	484
Sublease Income	$ (616)	$ (496)	$ (1,112)	$ (992)

Lease Cost Table Line Items

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- Definition

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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Amount of short-term lease cost, excluding expense for lease with term of one month or less.

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Amount of sublease income excluding finance and operating lease expense.

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Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

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