| **Consolidated Statements of Shareholders' Equity (unaudited) - USD ($) $ in Millions** | Total    | Common Stock | Additional Paid in Capital | Accumulated Other Comprehensive Loss | Treasury Stock at Cost | Retained Earnings |
|-----------------------------------------------------------------------------------------|----------|--------------|----------------------------|--------------------------------------|------------------------|-------------------|
| Balance at Beginning of Period at Dec. 31, 2013                                         | $ 9,184  | $ 4          | $ 3,463                    | $ (117)                              | $ (659)                | $ 6,493           |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                          |     |         |                       |                                 |                   |              |
| Net Income (Loss)                                                                       | 392      | 0            | 0                          | 0                                    | 0                      | 392               |
| Stock-based Compensation                                                                | 45       | 0            | 45                         | 0                                    | 0                      | 0                 |
| Exercise of Stock Options                                                               | 41       | 0            | 41                         | 0                                    | 0                      | 0                 |
| Dividends                                                                               | (116)    | 0            | 0                          | 0                                    | 0                      | (116)             |
| Changes in Treasury Stock, Net                                                          | (15)     | 0            | 0                          | 0                                    | (15)                   | 0                 |
| Tax Benefits Related to Exercise of Stock Options                                       | 17       | 0            | 17                         | 0                                    | 0                      | 0                 |
| Net Change in Pension and Other                                                         | 6        | 0            | 0                          | 6                                    | 0                      | 0                 |
| Balance at End of Period at Jun. 30, 2014                                               | 9,554    | 4            | 3,566                      | (111)                                | (674)                  | 6,769             |
| Balance at Beginning of Period at Dec. 31, 2014                                         | 10,325   | 4            | 3,624                      | (90)                                 | (671)                  | 7,458             |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                          |     |         |                       |                                 |                   |              |
| Net Income (Loss)                                                                       | (131)    | 0            | 0                          | 0                                    | 0                      | (131)             |
| Stock-based Compensation                                                                | 38       | 0            | 38                         | 0                                    | 0                      | 0                 |
| Exercise of Stock Options                                                               | 4        | 0            | 4                          | 0                                    | 0                      | 0                 |
| Dividends                                                                               | (134)    | 0            | 0                          | 0                                    | 0                      | (134)             |
| Changes in Treasury Stock, Net                                                          | (12)     | 0            | 0                          | 0                                    | (12)                   | 0                 |
| Issuance of Shares of Common Stock to Public, Net of Offering Costs                     | 1,112    | 0            | 1,112                      | 0                                    | 0                      | 0                 |
| Net Change in Pension and Other                                                         | 7        | 0            | 0                          | 7                                    | 0                      | 0                 |
| Balance at End of Period at Jun. 30, 2015                                               | $ 11,209 | $ 4          | $ 4,778                    | $ (83)                               | $ (683)                | $ 7,193           |

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| - Definition
Amount of increase in additional paid in capital (APIC) resulting from a tax benefit associated with share-based compensation plan other than an employee stock ownership plan (ESOP). Includes, but is not limited to, excess tax benefit.
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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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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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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
Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.
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| - Definition
Value of stock (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of stock value of such awards forfeited. Stock issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.
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| - Definition
Value of stock issued as a result of the exercise of stock options.
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Equity impact of the value of stock bought back by the entity at the exercise price or redemption price.
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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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