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Income Taxes (Schedule of Effective Income Tax Rate Calculation) (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | |
|---|---|---|
|
Mar. 31, 2015
|
Mar. 31, 2014
|
|
| Income Tax Disclosure [Abstract] | ||
| Income before income tax expense | $ 908 | $ 1,022 |
| Income tax expense | $ 322 | $ 391 |
| Effective income tax rate (in percent) | 35.50% | 38.30% |