FAIR VALUE (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Fair Value on a Recurring Basis [Member]
Financial Assets (Liabilities) [Abstract]
Cash equivalents and current investments	$ 79,249	$ 36,531
Other long-term assets	3,566	3,726
Forward contracts	0	158
Life insurance contracts	38,232	37,737
Financial assets (liabilities), net	121,047	78,152
Fair Value on a Recurring Basis [Member] \| Level 1 [Member]
Financial Assets (Liabilities) [Abstract]
Cash equivalents and current investments	79,249	36,531
Other long-term assets	3,566	3,726
Forward contracts	0	0
Life insurance contracts	0	0
Financial assets (liabilities), net	82,815	40,257
Fair Value on a Recurring Basis [Member] \| Level 2 [Member]
Financial Assets (Liabilities) [Abstract]
Cash equivalents and current investments	0	0
Other long-term assets	0	0
Forward contracts	0	158
Life insurance contracts	0	0
Financial assets (liabilities), net	0	158
Fair Value on a Recurring Basis [Member] \| Level 3 [Member]
Financial Assets (Liabilities) [Abstract]
Cash equivalents and current investments	0	0
Other long-term assets	0	0
Forward contracts	0	0
Life insurance contracts	38,232	37,737
Financial assets (liabilities), net	38,232	$ 37,737
Life Insurance Contracts [Member]
Changes in Fair Value of Level 3 Marketable Securities [Roll Forward]
Beginning balance	38,929
Actual Return on Plan Assets [Abstract]
Relating to assets still held at the reporting date	(633)
Purchases and issuances	0
Sales and settlements	(64)
Transfers into Level 3	0
Ending balance	$ 38,232

No definition available.

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- Definition

Fair value portion of cash equivalents with banks or financial institutions and current investments, including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

+ References

No definition available.

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Amount of purchases and issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

No definition available.

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Amount of sale and settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

No definition available.

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- Definition

Fair value portion of the amount that could be realized under a life insurance contract or contracts owned by the entity, commonly known as corporate-owned life insurance (COLI) or bank-owned life insurance (BOLI).

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- Definition

Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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Fair value of asset after deduction of liability.

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No definition available.

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- Definition

Fair value portion of asset contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward contracts, and swaps.

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Fair value portion of other assets.

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