| **Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (USD $)In Millions, unless otherwise specified** | Total    | Common stock [Member] | Additional paid-in capital [Member] | Retained earnings [Member] | Accumulated other comprehensive income (loss) [Member] | Treasury stock [Member] | Notes receivable for the issuance of common stock [Member] |
|--------------------------------------------------------------------------------------------------------------------------|----------|-----------------------|-------------------------------------|----------------------------|--------------------------------------------------------|-------------------------|------------------------------------------------------------|
| Balance at Dec. 31, 2011                                                                                                 |     | $ 683                 | $ 2,141                             | $ 8,308                    | $ 480                                                  | $ (102)                 | $ (22)                                                     |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                                                           |     |                  |                                |                       |                                                   |                    |                                                       |
| Net income (loss)                                                                                                        | 637      |                  |                                | 637                        |                                                   |                    |                                                       |
| Other comprehensive income (loss)                                                                                        | 650      |                  |                                |                       | 650                                                    |                    |                                                       |
| Dividends paid to common stockholders                                                                                    |     |                  |                                | (122)                      |                                                   |                    |                                                       |
| Stock-based compensation                                                                                                 |     |                  | 3                                   |                       |                                                   | 3                       |                                                       |
| (Increase) decrease in notes receivable from the issuance of common stock                                                |     |                  |                                |                       |                                                   |                    | 1                                                          |
| Balance at Sep. 30, 2012                                                                                                 | 12,660   | 683                   | 2,144                               | 8,823                      | 1,130                                                  | (99)                    | (21)                                                       |
| Balance at Dec. 31, 2012                                                                                                 | 12,314   | 683                   | 2,146                               | 8,774                      | 831                                                    | (99)                    | (21)                                                       |
| **Increase (Decrease) in Stockholders' Equity [Roll Forward]**                                                           |     |                  |                                |                       |                                                   |                    |                                                       |
| Net income (loss)                                                                                                        | 716      |                  |                                | 716                        |                                                   |                    |                                                       |
| Other comprehensive income (loss)                                                                                        | (718)    |                  |                                |                       | (718)                                                  |                    |                                                       |
| Dividends paid to common stockholders                                                                                    |     |                  |                                | (162)                      |                                                   |                    |                                                       |
| Stock-based compensation                                                                                                 |     |                  | (4)                                 |                       |                                                   | 8                       |                                                       |
| (Increase) decrease in notes receivable from the issuance of common stock                                                |     |                  |                                |                       |                                                   |                    | (1)                                                        |
| Balance at Sep. 30, 2013                                                                                                 | $ 12,153 | $ 683                 | $ 2,142                             | $ 9,328                    | $ 113                                                  | $ (91)                  | $ (22)                                                     |

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Stock-based compensation includes compensation expense as well as vesting and exercising of shares
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| - Definition
Equity impact of common stock cash dividends declared by an entity during the period. This element includes paid and unpaid dividends declared during the period.
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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
Net of tax amount of other comprehensive income (loss) attributable to the parent entity.
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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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