REVENUE - Contract Balances (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
REVENUE
Contract assets	$ 22,878	$ 18,838	$ 17,271
Contract liabilities	6,187	$ 6,480	$ 8,898
Revenue recognized, included in contract liability balance	$ 6,200

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Balance Type:	debit
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- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Publisher FASB
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Balance Type:	credit
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- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
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-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

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Balance Type:	credit
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- References

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration