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Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011
Cash equivalents and marketable securities |  |
Fair Value | $ 183,915 | $ 264,667
Amortized Cost | 183,926 | 264,767
Gross Unrealized Gains | 4 | 0
Gross Unrealized Losses | (15) | (100)
Cash, fair value | 19,415 | 24,789
Cash | 19,415 | 24,789
Cash, cash equivalents and marketable securities |  |
Fair Value | 203,330 | 289,456
Amortized Cost | 203,341 | 289,556
Gross Unrealized Gains | 4 | 0
Gross Unrealized Loss | (15) | (100)
Money market funds |  |
Cash equivalents and marketable securities |  |
Fair Value | 126,570 | 127,559
Amortized Cost | 126,570 | 127,559
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Weighted Rate of Return (as a percent) | 0.01% | 0.01%
Corporate notes, bonds and commercial paper |  |
Cash equivalents and marketable securities |  |
Maximum maturity period of available-for-sale securities (in years) | 3 years |
Maximum remaining maturity period of available-for-sale securities (in years) | 1 year |
Fair Value | 57,345 | 137,108
Amortized Cost | 57,356 | 137,208
Gross Unrealized Gains | 4 | 0
Gross Unrealized Losses | (15) | (100)
Weighted Rate of Return (as a percent) | 0.17% | 0.29%
Unrealized gain (loss), net |  |
Less than one year, Fair value | 51,819 | 137,108
Less than one year, Gross unrealized loss | (15) | (100)
Cash equivalents |  |
Cash equivalents and marketable securities |  |
Maximum remaining maturity period of available-for-sale securities (in years) | 1 year | 1 year
Fair Value | 129,569 | 137,455
Short term marketable securities |  |
Cash equivalents and marketable securities |  |
Fair Value | $ 54,346 | $ 127,212

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- Definition 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 includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. + References No definition available. + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 + Details
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