Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified |
Sep. 30, 2012
|
Dec. 31, 2011
|
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2 3/4 percent Convertible Senior Notes due 2019
|
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Assets measured at fair value on a recurring basis | ||
Interest rate on convertible debt (as a percent) | 2.75% | |
Significant Other Observable Inputs (Level 2) | 2 3/4 percent Convertible Senior Notes due 2019
|
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Assets measured at fair value on a recurring basis | ||
Fair value of convertible notes | $ 230,400 | |
Recurring basis | Total
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||
Assets measured at fair value on a recurring basis | ||
Cash equivalents | 82,863 | 58,892 |
Total assets | 345,063 | 338,361 |
Recurring basis | Total | Corporate debt securities
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Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | 190,648 | 166,922 |
Recurring basis | Total | Debt securities issued by U.S. government agencies
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Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | 31,151 | 80,440 |
Recurring basis | Total | Debt securities issued by the U.S. Treasury
|
||
Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | 13,486 | 2,356 |
Recurring basis | Total | Debt securities issued by states of the United States and political subdivisions of the states
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||
Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | 23,725 | 28,469 |
Recurring basis | Total | Equity securities
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||
Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | 3,190 | 1,282 |
Recurring basis | Quoted Prices in Active Markets (Level 1)
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Assets measured at fair value on a recurring basis | ||
Cash equivalents | 73,064 | 55,893 |
Total assets | 89,740 | 59,531 |
Recurring basis | Quoted Prices in Active Markets (Level 1) | Debt securities issued by the U.S. Treasury
|
||
Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | 13,486 | 2,356 |
Recurring basis | Quoted Prices in Active Markets (Level 1) | Equity securities
|
||
Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | 3,190 | 1,282 |
Recurring basis | Significant Other Observable Inputs (Level 2)
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||
Assets measured at fair value on a recurring basis | ||
Cash equivalents | 9,799 | 2,999 |
Total assets | 255,323 | 278,830 |
Recurring basis | Significant Other Observable Inputs (Level 2) | Corporate debt securities
|
||
Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | 190,648 | 166,922 |
Recurring basis | Significant Other Observable Inputs (Level 2) | Debt securities issued by U.S. government agencies
|
||
Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | 31,151 | 80,440 |
Recurring basis | Significant Other Observable Inputs (Level 2) | Debt securities issued by states of the United States and political subdivisions of the states
|
||
Assets measured at fair value on a recurring basis | ||
Available-for-sale securities | $ 23,725 | $ 28,469 |