| **Consolidated Statements of Stockholders' Equity $ in Millions**                 | USD ($)  |
|-----------------------------------------------------------------------------------|----------|
| Balance, beginning of year at Dec. 31, 2014                                       | $ 683    |
| Balance, end of period at Mar. 31, 2015                                           | 683      |
| Balance, beginning of year at Dec. 31, 2014                                       | 2,151    |
| **Additional Paid-In Capital**                                                    |     |
| Stock-based compensation                                                          | (8)      |
| Balance, end of period at Mar. 31, 2015                                           | 2,143    |
| Balance, beginning of year at Dec. 31, 2014                                       | 9,645    |
| **Retained Earnings (Accumulated Deficit)**                                       |     |
| Dividends paid to common stockholders                                             | (608)    |
| Net Income (Loss)                                                                 | 233      |
| Balance, end of period at Mar. 31, 2015                                           | 9,270    |
| Accumulated other comprehensive income (loss), beginning balance at Dec. 31, 2014 | 400      |
| **Accumulated Other Comprehensive Income (Loss)**                                 |     |
| Other Comprehensive Income (Loss)                                                 | 21       |
| Accumulated other comprehensive income (loss), ending balance at Mar. 31, 2015    | 421      |
| Balance, beginning of year at Dec. 31, 2014                                       | (84)     |
| **Treasury Stock**                                                                |     |
| Stock Based Compensation and Other                                                | 5        |
| Balance, end of period at Mar. 31, 2015                                           | (79)     |
| Balance, beginning of year at Dec. 31, 2014                                       | (1)      |
| Balance, end of period at Mar. 31, 2015                                           | (1)      |
| **Notes Receivable for the Issuance of Common Stock**                             |     |
| Total stockholder's equity                                                        | 12,437   |
| Total stockholder's equity                                                        | 11,756   |
| Balance, beginning of year at Dec. 31, 2015                                       | 683      |
| Balance, end of period at Mar. 31, 2016                                           | 683      |
| Balance, beginning of year at Dec. 31, 2015                                       | 2,153    |
| **Additional Paid-In Capital**                                                    |     |
| Stock-based compensation                                                          | (7)      |
| Balance, end of period at Mar. 31, 2016                                           | 2,146    |
| Balance, beginning of year at Dec. 31, 2015                                       | 9,313    |
| **Retained Earnings (Accumulated Deficit)**                                       |     |
| Dividends paid to common stockholders                                             | (609)    |
| Net Income (Loss)                                                                 | 66       |
| Balance, end of period at Mar. 31, 2016                                           | 8,770    |
| Accumulated other comprehensive income (loss), beginning balance at Dec. 31, 2015 | (315)    |
| **Accumulated Other Comprehensive Income (Loss)**                                 |     |
| Other Comprehensive Income (Loss)                                                 | 259      |
| Accumulated other comprehensive income (loss), ending balance at Mar. 31, 2016    | (56)     |
| Balance, beginning of year at Dec. 31, 2015                                       | (78)     |
| **Treasury Stock**                                                                |     |
| Stock Based Compensation and Other                                                | 5        |
| Balance, end of period at Mar. 31, 2016                                           | (73)     |
| Balance, beginning of year at Dec. 31, 2015                                       | 0        |
| Balance, end of period at Mar. 31, 2016                                           | 0        |
| **Notes Receivable for the Issuance of Common Stock**                             |     |
| Total stockholder's equity                                                        | $ 11,470 |

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Notes Receivable for the Issuance of Common Stock [Abstract]
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Stock-based compensation includes compensation expense as well as vesting and exercising of shares
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Stock Based Compensation and Other
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| - Definition
Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.
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| - Definition
Value received from shareholders in common stock-related transactions that are in excess of par value or stated value and amounts received from other stock-related transactions. Includes only common stock transactions (excludes preferred stock transactions). May be called contributed capital, capital in excess of par, capital surplus, or paid-in capital.
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| - Definition
Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity.
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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
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
Amounts receivable from officers and directors resulting from the sale of stock to officers or directors before the cash payment is received.
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The cumulative amount of the reporting entity's undistributed earnings or deficit.
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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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The amount allocated to treasury stock. Treasury stock is common and preferred shares of an entity that were issued, repurchased by the entity, and are held in its treasury.
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