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Summary of Contractual Maturities of Cash Equivalent and Marketable Fixed-Income Securities (Detail) (USD $)
In Millions, unless otherwise specified |
Dec. 31, 2012
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|---|---|
| Investments Classified by Contractual Maturity Date [Line Items] | |
| Amortized Cost | $ 8,934 |
| Estimated Fair Value | 8,950 |
|
Due within one year
|
|
| Investments Classified by Contractual Maturity Date [Line Items] | |
| Amortized Cost | 6,689 |
| Estimated Fair Value | 6,691 |
|
Due after one year through five years
|
|
| Investments Classified by Contractual Maturity Date [Line Items] | |
| Amortized Cost | 1,968 |
| Estimated Fair Value | 1,981 |
|
Due After Five Years
|
|
| Investments Classified by Contractual Maturity Date [Line Items] | |
| Amortized Cost | 277 |
| Estimated Fair Value | $ 278 |