| **Consolidated Statements Of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions**                  | Total   | Common Stock | Paid-In Capital | Retained Earnings | Accumulated Other Comprehensive Income | Treasury Stock | New Accounting Pronouncement, Early Adoption, Effect Retained Earnings | New Accounting Pronouncement, Early Adoption, Effect Accumulated Other Comprehensive Income |
|-------------------------------------------------------------------------------------------------------------------|---------|--------------|-----------------|-------------------|----------------------------------------|----------------|------------------------------------------------------------------------|---------------------------------------------------------------------------------------------|
| Beginning Balance at Dec. 31, 2014                                                                                |    | $ 397        | $ 1,214         | $ 4,505           | $ 1,744                                | $ (1,287)      |                                                                   |                                                                                        |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                                                    |    |         |            |              |                                   |           |                                                                   |                                                                                        |
| Share-based awards                                                                                                |    | 0            | (7)             |              |                                   | 41             |                                                                   |                                                                                        |
| Share-based compensation                                                                                          |    |         | 20              |              |                                   |           |                                                                   |                                                                                        |
| Other                                                                                                             |    |         | 5               |              |                                   | 7              |                                                                   |                                                                                        |
| Net Income                                                                                                        | $ 634   |         |            | 634               |                                   |           |                                                                   |                                                                                        |
| Dividends declared                                                                                                |    |         |            | (377)             |                                   |           |                                                                   |                                                                                        |
| Other comprehensive income (loss)                                                                                 | (400)   |         |            |              | (400)                                  |           |                                                                   |                                                                                        |
| Shares acquired - share repurchase authorization                                                                  |    |         |            |              |                                   | (53)           |                                                                   |                                                                                        |
| Shares acquired - share-based compensation plans                                                                  |    |         |            |              |                                   | (16)           |                                                                   |                                                                                        |
| Ending Balance at Dec. 31, 2015                                                                                   | 6,427   | $ 397        | 1,232           | 4,762             | 1,344                                  | (1,308)        |                                                                   |                                                                                        |
| Beginning Balance (in shares) at Dec. 31, 2014                                                                    |    | 163,700      |            |              |                                   |           |                                                                   |                                                                                        |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                                                    |    |         |            |              |                                   |           |                                                                   |                                                                                        |
| Share-based awards (in shares)                                                                                    |    | 1,300        |            |              |                                   |           |                                                                   |                                                                                        |
| Shares acquired—share repurchase authorization (in shares)                                                  |    | (1,000)      |            |              |                                   |           |                                                                   |                                                                                        |
| Shares acquired - share-based compensation plans (in shares)                                                      |    | (300)        |            |              |                                   |           |                                                                   |                                                                                        |
| Other (in shares)                                                                                                 |    | 200          |            |              |                                   |           |                                                                   |                                                                                        |
| Ending Balance (in shares) at Dec. 31, 2015                                                                       |    | 163,900      |            |              |                                   |           |                                                                   |                                                                                        |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                                                    |    |         |            |              |                                   |           |                                                                   |                                                                                        |
| Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02 |    |         |            |              |                                   |           | $ 0                                                                    | $ 0                                                                                         |
| Share-based awards                                                                                                |    | $ 0          | (8)             |              |                                   | 36             |                                                                   |                                                                                        |
| Share-based compensation                                                                                          |    |         | 23              |              |                                   |           |                                                                   |                                                                                        |
| Other                                                                                                             |    |         | 5               |              |                                   | 5              |                                                                   |                                                                                        |
| Net Income                                                                                                        | 591     |         |            | 591               |                                   |           |                                                                   |                                                                                        |
| Dividends declared                                                                                                |    |         |            | (316)             |                                   |           |                                                                   |                                                                                        |
| Other comprehensive income (loss)                                                                                 | 349     |         |            |              | 349                                    |           |                                                                   |                                                                                        |
| Shares acquired - share repurchase authorization                                                                  |    |         |            |              |                                   | (39)           |                                                                   |                                                                                        |
| Shares acquired - share-based compensation plans                                                                  |    |         |            |              |                                   | (13)           |                                                                   |                                                                                        |
| Ending Balance at Dec. 31, 2016                                                                                   | $ 7,060 | $ 397        | 1,252           | 5,037             | 1,693                                  | (1,319)        |                                                                   |                                                                                        |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                                                    |    |         |            |              |                                   |           |                                                                   |                                                                                        |
| Share-based awards (in shares)                                                                                    |    | 1,000        |            |              |                                   |           |                                                                   |                                                                                        |
| Shares acquired—share repurchase authorization (in shares)                                                  |    | (500)        |            |              |                                   |           |                                                                   |                                                                                        |
| Shares acquired - share-based compensation plans (in shares)                                                      |    | (200)        |            |              |                                   |           |                                                                   |                                                                                        |
| Other (in shares)                                                                                                 |    | 200          |            |              |                                   |           |                                                                   |                                                                                        |
| Ending Balance (in shares) at Dec. 31, 2016                                                                       | 198,300 | 164,400      |            |              |                                   |           |                                                                   |                                                                                        |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                                                    |    |         |            |              |                                   |           |                                                                   |                                                                                        |
| Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02 |    |         |            |              |                                   |           | 0                                                                      | 0                                                                                           |
| Share-based awards                                                                                                |    | $ 0          | (18)            |              |                                   | 26             |                                                                   |                                                                                        |
| Share-based compensation                                                                                          |    |         | 26              |              |                                   |           |                                                                   |                                                                                        |
| Other                                                                                                             |    |         | 5               |              |                                   | 5              |                                                                   |                                                                                        |
| Net Income                                                                                                        | $ 1,045 |         |            | 1,045             |                                   |           |                                                                   |                                                                                        |
| Dividends declared                                                                                                |    |         |            | (410)             |                                   |           |                                                                   |                                                                                        |
| Other comprehensive income (loss)                                                                                 | 603     |         |            |              | 603                                    |           |                                                                   |                                                                                        |
| Shares acquired - share repurchase authorization                                                                  |    |         |            |              |                                   | (92)           |                                                                   |                                                                                        |
| Shares acquired - share-based compensation plans                                                                  |    |         |            |              |                                   | (7)            |                                                                   |                                                                                        |
| Ending Balance at Dec. 31, 2017                                                                                   | $ 8,243 | $ 397        | $ 1,265         | $ 5,180           | $ 2,788                                | $ (1,387)      |                                                                   |                                                                                        |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                                                    |    |         |            |              |                                   |           |                                                                   |                                                                                        |
| Share-based awards (in shares)                                                                                    | 527     | 800          |            |              |                                   |           |                                                                   |                                                                                        |
| Shares acquired—share repurchase authorization (in shares)                                                  |    | (1,300)      |            |              |                                   |           |                                                                   |                                                                                        |
| Shares acquired - share-based compensation plans (in shares)                                                      |    | (100)        |            |              |                                   |           |                                                                   |                                                                                        |
| Other (in shares)                                                                                                 |    | 100          |            |              |                                   |           |                                                                   |                                                                                        |
| Ending Balance (in shares) at Dec. 31, 2017                                                                       | 198,300 | 163,900      |            |              |                                   |           |                                                                   |                                                                                        |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                                                    |    |         |            |              |                                   |           |                                                                   |                                                                                        |
| Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02 |    |         |            |              |                                   |           | $ (492)                                                                | $ 492                                                                                       |

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Shares Acquired During Period, Employee Share-Based Compensation Plans
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Shares Acquired During Period, Value, Employee Share-Based Compensation Plans
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| - Definition
Amount of increase to additional paid-in capital (APIC) from recognition of equity-based compensation.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.
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| - Definition
Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.
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No definition available.
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| - Definition
Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.
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| - Definition
A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.
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No definition available.
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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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| - Definition
Amount after tax and reclassification adjustments of other comprehensive income (loss).
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| - Definition
Number of shares of stock issued attributable to transactions classified as other.
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| - Definition
Number of share options (or share units) exercised during the current period.
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| - Definition
Value of stock issued as a result of the exercise of stock options.
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| - Definition
Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.
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This element represents movements included in the statement of changes in stockholders' equity which are not separately disclosed or provided for elsewhere in the taxonomy.
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| - Definition
Number of shares that have been repurchased during the period and are being held in treasury.
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| - Definition
Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.
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