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Property and Equipment - Additional Information (Detail) (USD $)
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12 Months Ended | 1 Months Ended | ||||||
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2012
Assets Held under Capital Leases
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Dec. 31, 2011
Assets Held under Capital Leases
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Dec. 31, 2012
Corporate Headquarters
Land and Buildings
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Dec. 31, 2012
Corporate Headquarters
Building
Property
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Dec. 31, 2012
Corporate Headquarters
Land
Property
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| Significant Acquisitions and Disposals [Line Items] | ||||||||
| Payment to acquire property and equipment | $ 3,785,000,000 | $ 1,811,000,000 | $ 979,000,000 | $ 1,200,000,000 | $ 210,000,000 | |||
| Number of property and equipment acquired | 11 | 3 | ||||||
| Property and equipment, estimated useful lives | 40 years | |||||||
| Depreciation expense on fixed assets including amortization | 1,653,000,000 | 1,034,000,000 | 552,000,000 | |||||
| Amortization of fixed assets acquired under capital lease obligations | 510,000,000 | 335,000,000 | 164,000,000 | |||||
| Gross assets remaining under leases | 2,300,000,000 | 1,600,000,000 | ||||||
| Accumulated depreciation associated with leases | 1,100,000,000 | 603,000,000 | ||||||
| Cash paid for interest on capital leases | $ 51,000,000 | $ 44,000,000 | $ 26,000,000 | |||||