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Financial Instruments (Details 3) (USD $)
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3 Months Ended | 9 Months Ended | ||
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Sep. 30, 2012
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Sep. 30, 2011
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Sep. 30, 2012
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Sep. 30, 2011
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| Proceeds from Marketable Debt Securities | ||||
| Proceeds from maturities and sales | $ 491,300,000 | $ 306,200,000 | $ 1,913,381,000 | $ 1,476,052,000 |
| Realized gains | 400,000 | 300,000 | 1,700,000 | 3,400,000 |
| Realized losses | $ (800,000) | $ (400,000) | $ (2,700,000) | $ (1,700,000) |
| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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