| **Stock-Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions**                                        | 12 Months Ended         |
|----------------------------------------------------------------------------------------------------------------------------------------|-------------------------|
||
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Number of shares authorized                                                                                                            | 11,000,000              |   |   |
| Number of shares available for grant                                                                                                   | 1,800,000               |   |   |
| Allocated share-based compensation expense                                                                                             | $ 32                    | $ 36 | $ 36 |
| Tax benefit from compensation expense                                                                                                  | 8                       | 18 | 12 |
| Compensation cost not yet recognized                                                                                                   | $ 44                    |   |   |
| Compensation cost not yet recognized, period for recognition                                                                           | 1 year 8 months 12 days |   |   |
| Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested in period, fair value | $ 16                    | $ 34 | $ 12 |
| Weighted average grant date fair value of awards granted (in usd per share)                                                            | $ 51.64                 | $ 44.20 | $ 32.27 |
| Performance Based Restricted Stock Units (RSUs)                                                                                        |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Award vesting period                                                                                                                   | 4 years                 |   |   |
| Performance Shares | Annual Performance Share Plan                                                                                     |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Measurement period of specific annual performance goals, in years                                                                      | 1 year                  |   |   |
| Cliff vesting period following date of grant                                                                                           | 2 years                 |   |   |
| Performance Shares | Long Term Incentive Plan                                                                                          |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Measurement period of specific annual performance goals, in years                                                                      | 3 years                 |   |   |
| Performance Shares | Special Supplemental Equity Awards                                                                                |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Service based vesting period                                                                                                           | 2 years                 |   |   |
| Minimum | Restricted Stock Units (RSUs)                                                                                                |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Award vesting period                                                                                                                   | 2 years                 |   |   |
| Minimum | Performance Based Restricted Stock Units (RSUs)                                                                              |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Award vesting rights, percentage                                                                                                       | 0.00%                   |   |   |
| Minimum | Performance Shares | Annual Performance Share Plan                                                                           |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Award vesting rights, percentage                                                                                                       | 0.00%                   |   |   |
| Minimum | Performance Shares | Long Term Incentive Plan                                                                                |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Award vesting rights, percentage                                                                                                       | 0.00%                   |   |   |
| Maximum | Restricted Stock Units (RSUs)                                                                                                |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Award vesting period                                                                                                                   | 3 years                 |   |   |
| Maximum | Performance Based Restricted Stock Units (RSUs)                                                                              |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Award vesting rights, percentage                                                                                                       | 100.00%                 |   |   |
| Maximum | Performance Shares | Annual Performance Share Plan                                                                           |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Award vesting rights, percentage                                                                                                       | 200.00%                 |   |   |
| Maximum | Performance Shares | Long Term Incentive Plan                                                                                |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                     |                    |   |   |
| Award vesting rights, percentage                                                                                                       | 200.00%                 |   |   |

| X                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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Cliff Vesting Period Following Date of Grant
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Measurement Period of Specific Annual Performance Goals, in Years
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Service Based Vesting Period
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| - Definition
Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.
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| - Definition
Unrecognized cost of unvested share-based compensation awards.
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| - Definition
Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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| - Definition
The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).
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| - Definition
Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.
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| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
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| - Definition
The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).
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| - Definition
The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.
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| - Definition
Percentage of vesting of share-based compensation awards.
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