CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Available for Sale Securities [Line Items]
Amortized Cost	$ 106,206	$ 114,247
Gross Unrealized Gains	16	25
Gross Unrealized Losses	(14)	(5)
Fair Value	106,208	114,267
Cash Equivalents [Member]
Available for Sale Securities [Line Items]
Amortized Cost	6,524	13,505
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	6,524	13,505
Short-Term Investments [Member]
Available for Sale Securities [Line Items]
Amortized Cost	99,682	100,742
Gross Unrealized Gains	16	25
Gross Unrealized Losses	(14)	(5)
Fair Value	99,684	100,762
Money Market Funds [Member]
Available for Sale Securities [Line Items]
Amortized Cost	6,524	13,505
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	6,524	13,505
Commercial Paper [Member]
Available for Sale Securities [Line Items]
Amortized Cost	11,186	9,696
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	11,186	9,696
U.S. Agency Securities [Member]
Available for Sale Securities [Line Items]
Amortized Cost	57,509	51,276
Gross Unrealized Gains	16	18
Gross Unrealized Losses	0	0
Fair Value	57,525	51,294
Corporate Bonds [Member]
Available for Sale Securities [Line Items]
Amortized Cost	30,987	34,751
Gross Unrealized Gains	0	5
Gross Unrealized Losses	(14)	(5)
Fair Value	30,973	34,751
U.S. Government Bonds [Member]
Available for Sale Securities [Line Items]
Amortized Cost		5,019
Gross Unrealized Gains		2
Gross Unrealized Losses		0
Fair Value		$ 5,021

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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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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