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Fair Value (Details) (USD $)
In Thousands, unless otherwise specified |
Jun. 30, 2012
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Dec. 31, 2011
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Fair Value, Inputs, Level 3 [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | ||
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Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | ||
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Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | ||
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Fair Value, Inputs, Level 3 [Member] | US Treasury Securities [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | ||
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Fair Value, Measurements, Recurring [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | 91,350 | 61,141 |
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Fair Value, Measurements, Recurring [Member] | Certificates of Deposit [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | 200 | 200 |
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Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | 7,408 | 9,238 |
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Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | 83,742 | 51,703 |
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Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | 7,608 | 9,438 |
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Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Certificates of Deposit [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | 200 | 200 |
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Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | 7,408 | 9,238 |
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Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | 83,742 | 51,703 |
|
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
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| Fair Value of financial assets on a recurring basis | ||
| Assets, Fair Value Disclosure, Recurring | $ 83,742 | $ 51,703 |