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Fair Value Measurements Fair Value Disclosure, Fair Value and Carrying Amounts (Details) (USD $)
In Billions, unless otherwise specified |
Dec. 31, 2011
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Dec. 31, 2010
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|---|---|---|
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Carrying value
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| Fair Value, Balance Sheet Grouping, Financial Statement Captions | ||
| Long-term Debt, Fair Value Disclosure | $ 4.5 | $ 3.5 |
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Estimated fair value
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| Fair Value, Balance Sheet Grouping, Financial Statement Captions | ||
| Long-term Debt, Fair Value Disclosure | $ 4.4 | $ 3.5 |