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Share-Based Payments - Data Related to All Restricted Stock Unit Activity (Detail) (Restricted Stock Units [Member], USD $)
In Millions, unless otherwise specified |
12 Months Ended | ||
|---|---|---|---|
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Dec. 31, 2011
Year
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Dec. 31, 2010
Year
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Dec. 31, 2009
Year
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Restricted Stock Units [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total grant date fair-value-based amount of shares vested | $ 279 | $ 311 | $ 131 |
| Total compensation cost related to nonvested RSU awards not yet recognized, pre-tax | $ 264 | $ 230 | $ 198 |
| Weighted-average period over which RSU cost is expected to be recognized (years) | 1.3 | 1.4 | 1.3 |