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Employee Benefit Plans - Fair Values Of Our Pension Plan Assets (Parenthetical) (Detail) (Level 3 [Member], USD $)
In Millions, unless otherwise specified |
Dec. 31, 2011
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Dec. 31, 2010
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|---|---|---|
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Level 3 [Member]
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| Pension Plans, Postretirement and Other Employee Benefits [Line Items] | ||
| Fair value of participating interest in debt security | $ 144 | $ 92 |
| Net receivables related to security transactions | $ 19 | $ 15 |