SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Available-for-sale Investments) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 114,492	$ 112,068
Gross unrealized loss	45	26
Gross unrealized gains	128	236
Estimated fair market value	114,575us-gaap_AvailableForSaleSecurities	112,278us-gaap_AvailableForSaleSecurities
Cash Equivalents due in less than 3 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost		3,098
Gross unrealized loss		0
Gross unrealized gains		1
Estimated fair market value		3,099
Investments due in 4-12 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	30,233	6,007
Gross unrealized loss	0	0
Gross unrealized gains	36	33
Estimated fair market value	30,269	6,040
Investments due in more than 12 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	84,259	102,963
Gross unrealized loss	45	26
Gross unrealized gains	92	202
Estimated fair market value	84,306	103,139
Commercial paper [Member] \| Cash Equivalents due in less than 3 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost		3,098
Gross unrealized loss		0
Gross unrealized gains		1
Estimated fair market value		3,099
Corporate securities [Member] \| Investments due in 4-12 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	30,233	6,007
Gross unrealized loss	0	0
Gross unrealized gains	36	33
Estimated fair market value	30,269	6,040
Corporate securities [Member] \| Investments due in more than 12 months [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	84,259	102,963
Gross unrealized loss	45	26
Gross unrealized gains	92	202
Estimated fair market value	$ 84,306	$ 103,139

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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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

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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