FAIR VALUE MEASUREMENTS (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Included in cash and cash equivalents
Amortized Cost	$ 7,231us-gaap_CashEquivalentsAtCarryingValue	$ 40,342us-gaap_CashEquivalentsAtCarryingValue
Estimated Fair Value	7,231	40,342
Restricted cash
Amortized Cost	266	266
Estimated Fair Value	266	266
Marketable securities
Amortized Cost	153,411	127,661
Gross Unrealized Gains	45	16
Gross Unrealized Losses	(62)	(100)
Estimated Fair Value	153,394us-gaap_AvailableForSaleSecurities	127,577us-gaap_AvailableForSaleSecurities
Money market funds
Included in cash and cash equivalents
Amortized Cost	7,231	40,342
Estimated Fair Value	7,231	40,342
Certificates of deposit
Restricted cash
Amortized Cost	266	266
Estimated Fair Value	266	266
Government-sponsored enterprise securities (due in less than 1 year)
Marketable securities
Amortized Cost	401	401
Gross Unrealized Losses	(1)	(1)
Estimated Fair Value	400	400
Government-sponsored enterprise securities (due in 1 to 2 years)
Marketable securities
Amortized Cost	5,806	6,556
Gross Unrealized Losses	(1)	(7)
Estimated Fair Value	5,805	6,549
Commercial paper (due in less than 1 year)
Marketable securities
Amortized Cost	28,963	10,985
Gross Unrealized Gains	33	14
Estimated Fair Value	28,996	10,999
Corporate notes (due in less than 1 year)
Marketable securities
Amortized Cost	106,305	97,307
Gross Unrealized Gains	10	2
Gross Unrealized Losses	(56)	(63)
Estimated Fair Value	106,259	97,246
Corporate notes (due in 1 to 2 years)
Marketable securities
Amortized Cost	11,936	12,412
Gross Unrealized Gains	2
Gross Unrealized Losses	(4)	(29)
Estimated Fair Value	$ 11,934	$ 12,383

Amount of gross unrealized gains from available-for-sale securities as of the reporting date.

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Amount of gross unrealized losses from available-for-sale securities as of the reporting date.

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

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-Publisher FASB

-Name Accounting Standards Codification

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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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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. For a classified balance sheet represents the current portion only (the noncurrent portion has a separate concept); there is a separate and distinct element for unclassified presentations.

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The aggregate value of all restricted investments.

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