| **Income Taxes**                     | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
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| **Income Tax Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Income Taxes                         | INCOME TAXES As of March 31, 2013, and December 31, 2012, we had no liability for unrecognized tax benefits. Details about our liability for unrecognized tax benefits are found in our 2012 Annual Report on Form 10-K, Item 8, Note 11, Income Taxes, Page 129. The differences between the 35 percent statutory income tax rate and our effective income tax rate were as follows: (Dollars in millions) Three months ended March 31,  2013 2012Tax at statutory rate $76 35.0 % $39 35.0 %Increase (decrease) resulting from:        Tax-exempt income from municipal bonds (8) (3.7) (8) (7.6)Dividend received exclusion (6) (2.6) (6) (4.8)Other 1 0.3 1 0.6Provision for income taxes $63 29.0 % $26 23.2 % The change in our effective tax rate was primarily due to changes in pretax income from underwriting results and realized investment gains and losses, compared with unchanged levels of permanent book-tax differences. |

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| - Definition
The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.
+ References
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