| **Segment Information (Tables)** | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
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| **Segment Reporting [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Segment Information              | Segment information is summarized in the following table: (Dollars in millions) Three months ended September 30, Nine months ended September 30,  2015 2014 2015 2014Revenues:        Commercial lines insurance        Commercial casualty $257 $237 $753 $695Commercial property 205 186 604 537Commercial auto 141 133 416 391Workers' compensation 93 93 276 280Other commercial  61 71 186 223Commercial lines insurance premiums 757 720 2,235 2,126Fee revenues 1 1 3 3Total commercial lines insurance 758 721 2,238 2,129         Personal lines insurance        Personal auto 128 121 376 354Homeowner 117 110 345 330Other personal 32 32 96 91Personal lines insurance premiums 277 263 817 775Fee revenues 1 1 2 2Total personal lines insurance 278 264 819 777         Excess and surplus lines insurance 42 42 124 109Fee revenues — — 1 —Total excess and surplus lines insurance 42 42 125 109         Life insurance premiums 51 46 156 147Separate account investment management fees 2 1 4 4Total life insurance 53 47 160 151         Investments            Investment income, net of expenses 143 138 422 409    Realized investment gains, net 3 65 110 101Total investment revenue 146 203 532 510         Other 1 3 5 7Total revenues $1,278 $1,280 $3,879 $3,683         Income (loss) before income taxes:        Insurance underwriting results        Commercial lines insurance $121 $67 $244 $97Personal lines insurance (2) 14 (30) (33)Excess and surplus lines insurance 14 13 29 22Life insurance 1 (4) (1) (5)Investments 125 182 468 448Other (16) (13) (45) (44)Total income before income taxes $243 $259 $665 $485Identifiable assets: September 30, 2015 December 31, 2014Property casualty insurance $2,568 $2,656Life insurance 1,328 1,316Investments 14,476 14,441Other 379 340Total $18,751 $18,753      |

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| - Definition
Tabular disclosure of the profit or loss and total assets for each reportable segment. An entity discloses certain information on each reportable segment if the amounts (a) are included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) are otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.
+ References
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| - References
No definition available.
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