Annual report pursuant to Section 13 and 15(d)

Activity in Accumulated Other Comprehensive Income (Loss) (Detail)

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Activity in Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Balance at beginning of year $ (2,635) $ (1,717)  
Current period changes in fair value (net of tax effect of $(16), $(4), and $4) 35 (39) (93)
Current period changes in fair value (net of tax effect of $11, $17, and $3) (6) 39 33
Aggregate adjustment for the year (net of tax effect of $11, $(34), and $(27)) (92) (105) 75
Balance at end of period (3,103) (2,635) (1,717)
Foreign currency translation gain (loss)
      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Balance at beginning of year (68) 37 (38)
Aggregate adjustment for the year (net of tax effect of $11, $(34), and $(27)) (92) (105) 75
Balance at end of period (160) (68) 37
Unrealized gain (loss) on marketable securities, net of tax
      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Balance at beginning of year 12 (27) (60)
Current period changes in fair value (net of tax effect of $11, $17, and $3) 18 30 25
Reclassification to earnings (net of tax effect of $(14), $6, and $5) (24) 9 8
Balance at end of period 6 12 (27)
Unrealized gain (loss) on cash flow hedges, net of tax
      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Balance at beginning of year (239) (200) (107)
Current period changes in fair value (net of tax effect of $(16), $(4), and $4) (26) (7) 6
Reclassification to earnings (net of tax effect of $37, $(19) and $(60)) 61 (32) (99)
Balance at end of period (204) (239) (200)
Unrecognized pension and postretirement benefit costs, net of tax
      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Balance at beginning of year (2,340) (1,527) (2,211)
Reclassification to earnings (net of tax effect of $378, $150 and $197) 628 245 329
Net actuarial gain (loss) and prior service cost resulting from remeasurements of plan assets and liabilities (net of tax effect of $(622), $(633), and $219) (1,033) (1,058) 355
Balance at end of period $ (2,745) $ (2,340) $ (1,527)