Investments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Amortized cost and fair value of marketable securities
Amortized Cost	$ 27,527	$ 17,483
Gross unrealized gains	14	1
Gross unrealized losses	(2)	(2)
Fair Value	27,539	17,482
Cash and Cash Equivalents [Member]
Amortized cost and fair value of marketable securities
Fair Value	9,744	2,768
Marketable securities [Member]
Amortized cost and fair value of marketable securities
Fair Value	17,590	14,509
Restricted cash [Member]
Amortized cost and fair value of marketable securities
Fair Value	205	205
Money market funds [Member]
Amortized cost and fair value of marketable securities
Amortized Cost	9,949	2,973
Fair Value	9,949	2,973
Commercial paper [Member]
Amortized cost and fair value of marketable securities
Amortized Cost	4,235
Gross unrealized gains	13
Fair Value	4,248
Corporate securities [Member]
Amortized cost and fair value of marketable securities
Amortized Cost	4,516	6,024
Gross unrealized gains	1
Gross unrealized losses		(2)
Fair Value	4,517	6,022
U.S. government-backed securities [Member]
Amortized cost and fair value of marketable securities
Amortized Cost	8,321	5,435
Gross unrealized gains		1
Gross unrealized losses	(2)
Fair Value	8,319	5,436
U.S. treasury note [Member]
Amortized cost and fair value of marketable securities
Amortized Cost	506	3,051
Fair Value	$ 506	$ 3,051

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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