| Carrying Value of Outstanding Debt (Detail) (USD $)In Millions, unless otherwise specified
 | 6 Months Ended |  | 
      
        | Jun. 30, 2013 | Dec. 31, 2012 | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | $ 11,720 |  | 
      
        | Long-term Debt and Capital Lease Obligations | 11,923 | 12,870 | 
      
        | Less current maturities | (1,086) | (1,781) | 
      
        | Long-Term Debt | 10,837 | 11,089 | 
      
        | 4.50% stated rate |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 1,750 |  | 
      
        | Debt instrument, stated interest rate | 4.50% |  | 
      
        | 3.875% stated rate |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 1,000 |  | 
      
        | Debt instrument, stated interest rate | 3.875% |  | 
      
        | Commercial Paper |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 1,045 |  | 
      
        | Maturity - Minimum Date | Dec. 31,
				 2013 |  | 
      
        | Maturity - Maximum Date | Dec. 31,
				 2013 |  | 
      
        | Total debt | 1,045 | 0 | 
      
        | Senior notes | 4.50% stated rate |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 0 |  | 
      
        | Maturity - Maximum Date | Jan. 15,
				 2013 |  | 
      
        | Debt instrument, stated interest rate | 4.50% |  | 
      
        | Total debt | 0 | 1,751 | 
      
        | Senior notes | 3.875% stated rate |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 1,000 |  | 
      
        | Maturity - Maximum Date | Apr. 15,
				 2014 |  | 
      
        | Debt instrument, stated interest rate | 3.875% |  | 
      
        | Total debt | 1,020 | 1,033 | 
      
        | Senior notes | 5.50% stated rate |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 750 |  | 
      
        | Maturity - Maximum Date | Jan. 15,
				 2018 |  | 
      
        | Debt instrument, stated interest rate | 5.50% |  | 
      
        | Total debt | 823 | 851 | 
      
        | Senior notes | 5.125% stated rate |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 1,000 |  | 
      
        | Maturity - Maximum Date | Apr. 15,
				 2019 |  | 
      
        | Debt instrument, stated interest rate | 5.125% |  | 
      
        | Total debt | 1,090 | 1,140 | 
      
        | Senior notes | Debentures 8 Point 375 Percent Due 2030 [Member] |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 276 |  | 
      
        | Total debt | 283 | 284 | 
      
        | Senior notes | 3.125% stated rate |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 1,500 |  | 
      
        | Maturity - Maximum Date | Jan. 15,
				 2021 |  | 
      
        | Debt instrument, stated interest rate | 3.125% |  | 
      
        | Total debt | 1,606 | 1,655 | 
      
        | Senior notes | 6.20% stated rate |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 1,500 |  | 
      
        | Maturity - Maximum Date | Jan. 15,
				 2038 |  | 
      
        | Debt instrument, stated interest rate | 6.20% |  | 
      
        | Total debt | 1,481 | 1,480 | 
      
        | Senior notes | 4.875% stated rate |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 500 |  | 
      
        | Maturity - Maximum Date | Nov. 15,
				 2040 |  | 
      
        | Debt instrument, stated interest rate | 4.875% |  | 
      
        | Total debt | 489 | 489 | 
      
        | Senior notes | A1125SeniorNotes [Member] |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 375 |  | 
      
        | Maturity - Maximum Date | Oct.
				01,
				 2017 |  | 
      
        | Debt instrument, stated interest rate | 1.125% |  | 
      
        | Total debt | 365 | 373 | 
      
        | Senior notes | 2.45% senior notes [Member] |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 1,000 |  | 
      
        | Maturity - Maximum Date | Oct.
				01,
				 2022 |  | 
      
        | Debt instrument, stated interest rate | 2.45% |  | 
      
        | Total debt | 934 | 996 | 
      
        | Senior notes | 3.625% senior notes [Member] |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 375 |  | 
      
        | Maturity - Maximum Date | Oct.
				01,
				 2042 |  | 
      
        | Debt instrument, stated interest rate | 3.625% |  | 
      
        | Total debt | 367 | 367 | 
      
        | Senior notes | Debentures 8 Point 375 Percent Due 2020 [Member] |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 424 |  | 
      
        | Total debt | 486 | 512 | 
      
        | Senior notes | Floating rate senior notes |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 377 |  | 
      
        | Maturity - Minimum Date | Jan.
				01,
				 2049 |  | 
      
        | Maturity - Maximum Date | Jan.
				01,
				 2053 |  | 
      
        | Total debt | 373 | 374 | 
      
        | Debentures [Member] | 8.375% debentures due 2030 [Member] |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Maturity - Maximum Date | Jan.
				01,
				 2030 |  | 
      
        | Debt instrument, stated interest rate | 8.375% |  | 
      
        | Debentures [Member] | 8.375% debentures due 2020 [Member] |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Maturity - Minimum Date | Jan.
				01,
				 2020 |  | 
      
        | Debt instrument, stated interest rate | 8.375% |  | 
      
        | Facility notes and bonds |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 320 |  | 
      
        | Maturity - Minimum Date | Jan.
				01,
				 2015 |  | 
      
        | Maturity - Maximum Date | Jan.
				01,
				 2036 |  | 
      
        | Total debt | 320 | 320 | 
      
        | Pound Sterling notes |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Maturity - Minimum Date | Jan.
				01,
				 2031 |  | 
      
        | Maturity - Maximum Date | Jan.
				01,
				 2050 |  | 
      
        | Pound Sterling notes | Pound Sterling Notes 5 Point 5 Percent [Member] |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 101 |  | 
      
        | Total debt | 97 | 103 | 
      
        | Pound Sterling notes | Pound Sterling Notes 5 Point 13 Percent [Member] |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 693 |  | 
      
        | Total debt | 660 | 699 | 
      
        | Capital Lease Obligations |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 481 |  | 
      
        | Maturity - Minimum Date | Dec. 31,
				 2013 |  | 
      
        | Maturity - Maximum Date | Jan.
				01,
				 3004 |  | 
      
        | Total debt | 481 | 440 | 
      
        | Other debt |  |  | 
      
        | Debt Instrument [Line Items] |  |  | 
      
        | Debt Instrument, Face Amount | 3 |  | 
      
        | Maturity - Minimum Date | Jan.
				01,
				 2013 |  | 
      
        | Maturity - Maximum Date | Jan.
				01,
				 2022 |  | 
      
        | Total debt | $ 3 | $ 3 |