FAIR VALUE MEASUREMENTS - SECURITY TYPE (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Included in cash and cash equivalents
Amortized Cost	$ 19,177	$ 40,342
Gross Unrealized Losses	(1)
Estimated Fair Value	19,176	40,342
Restricted cash
Amortized Cost	267	266
Estimated Fair Value	267	266
Marketable securities
Amortized Cost	125,397	127,661
Gross Unrealized Gains	50	16
Gross Unrealized Losses	(262)	(100)
Estimated Fair Value	125,185	127,577
Money market funds
Included in cash and cash equivalents
Amortized Cost	4,577	40,342
Estimated Fair Value	4,577	40,342
Commercial paper
Included in cash and cash equivalents
Amortized Cost	7,599
Estimated Fair Value	7,599
Government-sponsored enterprise securities
Included in cash and cash equivalents
Amortized Cost	1,999
Estimated Fair Value	1,999
Corporate notes
Included in cash and cash equivalents
Amortized Cost	5,002
Gross Unrealized Losses	(1)
Estimated Fair Value	5,001
Certificate of deposit
Restricted cash
Amortized Cost	267	266
Estimated Fair Value	267	266
Government-sponsored enterprise securities (due in less than 1 year)
Marketable securities
Amortized Cost		401
Gross Unrealized Losses		(1)
Estimated Fair Value		400
Government-sponsored enterprise securities (due in 1 to 2 years)
Marketable securities
Amortized Cost	10,007	6,556
Gross Unrealized Losses	(57)	(7)
Estimated Fair Value	9,950	6,549
Commercial paper (due in less than 1 year)
Marketable securities
Amortized Cost	27,661	10,985
Gross Unrealized Gains	49	14
Gross Unrealized Losses	(2)
Estimated Fair Value	27,708	10,999
Corporate notes (due in less than 1 year)
Marketable securities
Amortized Cost	64,892	97,307
Gross Unrealized Gains	1	2
Gross Unrealized Losses	(77)	(63)
Estimated Fair Value	64,816	97,246
Corporate notes (due in 1 to 2 years)
Marketable securities
Amortized Cost	22,837	12,412
Gross Unrealized Losses	(126)	(29)
Estimated Fair Value	$ 22,711	$ 12,383

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

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

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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 aggregate value of all restricted investments.

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