| **Quarterly Supplementary Data (Details) - USD ($) $ / shares in Units, $ in Millions** | 3 Months Ended | 12 Months Ended |
|-----------------------------------------------------------------------------------------|----------------|-----------------|
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| **Quarterly Financial Information Disclosure [Abstract]**                               |           |            |   |   |   |   |   |   |   |   |   |
| Revenues                                                                                | $ 1,411        | $ 1,412         | $ 1,386 | $ 1,523 | $ 1,312 | $ 1,402 | $ 1,371 | $ 1,364 | $ 5,732 | $ 5,449 | $ 5,142 |
| Income before income taxes                                                              | 197            | 129             | 128 | 276 | 128 | 253 | 166 | 265 | 730 | 812 | 881 |
| Net Income (Loss) Attributable to Parent                                                | $ 642          | $ 102           | $ 100 | $ 201 | $ 100 | $ 180 | $ 123 | $ 188 | $ 1,045 | $ 591 | $ 634 |
| Basic (in usd per share)                                                                | $ 3.92         | $ 0.62          | $ 0.61 | $ 1.22 | $ 0.61 | $ 1.09 | $ 0.75 | $ 1.14 | $ 6.36 | $ 3.59 | $ 3.87 |
| Diluted (in usd per share)                                                              | $ 3.88         | $ 0.61          | $ 0.60 | $ 1.21 | $ 0.60 | $ 1.08 | $ 0.74 | $ 1.13 | $ 6.29 | $ 3.55 | $ 3.83 |

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| - Definition
The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.
+ References
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| - Definition
The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.
+ References
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| - Definition
Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.
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| - Definition
The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.
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No definition available.
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| - Definition
Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).
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