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Commitments and Contingencies - Additional Durational Information (Detail) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
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Mar. 31, 2011
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2009
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| Commitments and Contingencies Disclosure [Line Items] | ||||
| Rent expense under operating leases, including co-location arrangements | $ 380 | $ 293 | $ 323 | |
| Charge related to resolution of investigation | $ 500 | $ 500 | $ 0 | $ 0 |
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Minimum
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| Commitments and Contingencies Disclosure [Line Items] | ||||
| Operating lease, expiration date | 2012 | |||
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Maximum
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| Commitments and Contingencies Disclosure [Line Items] | ||||
| Operating lease, expiration date | 2063 | |||