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Wireless Licenses, Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $)
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12 Months Ended | |
|---|---|---|
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Dec. 31, 2014
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Dec. 31, 2013
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| Indefinite-lived Intangible Assets [Line Items] | ||
| Wireless licenses (current assets) held-for-sale | $ 300,000,000 | $ 900,000,000 |
| Wireless licenses under development | 4,580,000,000 | 4,176,000,000 |
| Average remaining renewal period of wireless license portfolio (in years) | 4 years 8 months 12 days | |
| Wireless Licenses | ||
| Indefinite-lived Intangible Assets [Line Items] | ||
| Wireless licenses under development | $ 400,000,000 | $ 7,700,000,000 |