Short-Term and Long-Term Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 10,681	$ 21,239
Gross Unrealized Gains	4	21
Gross Unrealized Losses	(5)	(8)
Fair Value	10,680	21,252
Long-term Investments \| Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,592	16,132
Gross Unrealized Gains	2	16
Gross Unrealized Losses	(4)	(7)
Fair Value	7,590	16,141
Long-term Investments \| Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,066	2,069
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	0
Fair Value	2,068	2,070
Long-term Investments \| Foreign bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,023	3,038
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(1)	(1)
Fair Value	1,022	3,041
Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,946	28,473
Gross Unrealized Gains	31	17
Gross Unrealized Losses	(2)	(5)
Fair Value	37,975	28,485
Short-term Investments \| Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,145	18,767
Gross Unrealized Gains	21	7
Gross Unrealized Losses	(2)	(4)
Fair Value	27,164	18,770
Short-term Investments \| Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,749	4,646
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Fair Value	2,749	4,647
Short-term Investments \| Foreign bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,052	5,060
Gross Unrealized Gains	10	9
Gross Unrealized Losses	0	(1)
Fair Value	$ 8,062	$ 5,068

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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