LEASES - Lease expense (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
LEASES
Amortization of right-of-use assets	$ 704	$ 14,608
Interest on lease liabilities	377	2,085
Operating lease cost	3,873	9,169
Short-term lease cost	84	464
Variable lease cost	1,375	1,360
Total lease cost	6,413	27,686
Rental expense	$ 5,200	$ 11,000	$ 14,900

Amount of interest expense on finance lease liability.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

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- Definition

Amount of lease cost recognized by lessee for lease contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
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- References

No definition available.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
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Balance Type:	debit
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- Definition

Amount of operating lease expense. Excludes sublease income.

+ References

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-Publisher FASB
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-SubTopic 20
-Section 45
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- Definition

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

+ References

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- Definition

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

+ References

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