CASH, CASH EQUIVALENTS AND SHORT TERM INVESTMENTS (Schedule of Cash, Cash Equivalents and Short Term Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Line Items]
Cost	$ 72,451	$ 33,546
Gross Unrealized Gains	163	69
Gross Unrealized Losses	(392)	(119)
Estimated fair value	72,222	33,496
Cash [Member]
Cash And Cash Equivalents [Line Items]
Cost	24,454	9,166
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated fair value	24,454	9,166
Money market funds [Member]
Cash And Cash Equivalents [Line Items]
Cost	200	457
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated fair value	200	457
Government and agency securities [Member]
Cash And Cash Equivalents [Line Items]
Cost	42,220	19,132
Gross Unrealized Gains	135	51
Gross Unrealized Losses	(355)	(96)
Estimated fair value	42,000	19,087
Corporate debt securities [Member]
Cash And Cash Equivalents [Line Items]
Cost	5,577	4,791
Gross Unrealized Gains	28	18
Gross Unrealized Losses	(37)	(23)
Estimated fair value	$ 5,568	$ 4,786

Cost of cash cash equivalent or marketable security.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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