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Stock-based compensation Stock-based compensation (Details) (USD $)
In Millions, unless otherwise specified |
12 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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| Components of stock-based compensation expense [Abstract] | |||
| Total stock-based compensation expense, pre-tax | $ 362 | $ 341 | $ 353 |
| Tax benefit from stock-based compensation expense | (134) | (124) | (120) |
| Total stock-based compensation expense, net of tax | 228 | 217 | 233 |
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Stock Options [Member]
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| Components of stock-based compensation expense [Abstract] | |||
| Total stock-based compensation expense, pre-tax | 59 | 85 | 124 |
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Restricted Stock Units [Member]
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| Components of stock-based compensation expense [Abstract] | |||
| Total stock-based compensation expense, pre-tax | 186 | 188 | 182 |
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Performance Units [Member]
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| Components of stock-based compensation expense [Abstract] | |||
| Total stock-based compensation expense, pre-tax | $ 117 | $ 68 | $ 47 |