| **Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions** | 12 Months Ended |
|----------------------------------------------------------------------------------------|-----------------|
||
| **Segment Reporting Information [Line Items]**                                         |            |   |   |
| Net written premiums                                                                   | $ 6,962         | $ 7,088 | $ 7,348 |
| **Operating Revenues**                                                                 |            |   |   |
| Net earned premiums                                                                    | 6,921           | 7,212 | 7,271 |
| Net investment income                                                                  | 1,840           | 2,067 | 2,282 |
| Other revenues                                                                         | 407             | 356 | 359 |
| Total operating revenues                                                               | 9,168           | 9,635 | 9,912 |
| **Claims, Benefits and Expenses**                                                      |            |   |   |
| Net incurred claims and benefits                                                       | 5,372           | 5,577 | 5,793 |
| Policyholders' dividends                                                               | 12              | 14 | 13 |
| Amortization of deferred acquisition costs                                             | 1,540           | 1,317 | 1,362 |
| Other insurance related expenses                                                       | 1,093           | 1,029 | 1,013 |
| Other expenses                                                                         | 535             | 548 | 475 |
| Total claims, benefits and expenses                                                    | 8,552           | 8,485 | 8,656 |
| Operating income (loss) from continuing operations before income tax                   | 616             | 1,150 | 1,256 |
| Income tax (expense) benefit on operating income (loss)                                | (101)           | (301) | (355) |
| Net operating income (loss) from continuing operations                                 | 515             | 849 | 901 |
| Net realized investment gains (losses), pre-tax                                        | (67)            | 57 | 20 |
| Income tax (expense) benefit on net realized investment gains (losses)                 | 31              | (18) | (6) |
| Net realized investment gains (losses), after tax                                      | (36)            | 39 | 14 |
| Net income (loss) from continuing operations                                           | 479             | 888 | 915 |
| Specialty [Member]                                                                     |            |   |   |
| **Segment Reporting Information [Line Items]**                                         |            |   |   |
| Net written premiums                                                                   | 2,781           | 2,839 | 2,880 |
| **Operating Revenues**                                                                 |            |   |   |
| Net earned premiums                                                                    | 2,782           | 2,838 | 2,795 |
| Net investment income                                                                  | 474             | 560 | 629 |
| Other revenues                                                                         | 356             | 295 | 257 |
| Total operating revenues                                                               | 3,612           | 3,693 | 3,681 |
| **Claims, Benefits and Expenses**                                                      |            |   |   |
| Net incurred claims and benefits                                                       | 1,597           | 1,627 | 1,593 |
| Policyholders' dividends                                                               | 4               | 6 | 6 |
| Amortization of deferred acquisition costs                                             | 589             | 592 | 585 |
| Other insurance related expenses                                                       | 278             | 262 | 250 |
| Other expenses                                                                         | 301             | 254 | 237 |
| Total claims, benefits and expenses                                                    | 2,769           | 2,741 | 2,671 |
| Operating income (loss) from continuing operations before income tax                   | 843             | 952 | 1,010 |
| Income tax (expense) benefit on operating income (loss)                                | (283)           | (318) | (342) |
| Net operating income (loss) from continuing operations                                 | 560             | 634 | 668 |
| Net realized investment gains (losses), pre-tax                                        | (33)            | 15 | (5) |
| Income tax (expense) benefit on net realized investment gains (losses)                 | 11              | (5) | 2 |
| Net realized investment gains (losses), after tax                                      | (22)            | 10 | (3) |
| Net income (loss) from continuing operations                                           | 538             | 644 | 665 |
| Commercial [Member]                                                                    |            |   |   |
| **Segment Reporting Information [Line Items]**                                         |            |   |   |
| Net written premiums                                                                   | 2,818           | 2,817 | 2,960 |
| **Operating Revenues**                                                                 |            |   |   |
| Net earned premiums                                                                    | 2,788           | 2,906 | 3,004 |
| Net investment income                                                                  | 593             | 723 | 899 |
| Other revenues                                                                         | 37              | 38 | 96 |
| Total operating revenues                                                               | 3,418           | 3,667 | 3,999 |
| **Claims, Benefits and Expenses**                                                      |            |   |   |
| Net incurred claims and benefits                                                       | 1,814           | 2,187 | 2,259 |
| Policyholders' dividends                                                               | 8               | 8 | 7 |
| Amortization of deferred acquisition costs                                             | 469             | 493 | 526 |
| Other insurance related expenses                                                       | 538             | 487 | 498 |
| Other expenses                                                                         | 28              | 31 | 32 |
| Total claims, benefits and expenses                                                    | 2,857           | 3,206 | 3,322 |
| Operating income (loss) from continuing operations before income tax                   | 561             | 461 | 677 |
| Income tax (expense) benefit on operating income (loss)                                | (192)           | (154) | (229) |
| Net operating income (loss) from continuing operations                                 | 369             | 307 | 448 |
| Net realized investment gains (losses), pre-tax                                        | (47)            | 16 | (15) |
| Income tax (expense) benefit on net realized investment gains (losses)                 | 16              | (6) | 5 |
| Net realized investment gains (losses), after tax                                      | (31)            | 10 | (10) |
| Net income (loss) from continuing operations                                           | 338             | 317 | 438 |
| International [Member]                                                                 |            |   |   |
| **Segment Reporting Information [Line Items]**                                         |            |   |   |
| Net written premiums                                                                   | 822             | 880 | 959 |
| **Operating Revenues**                                                                 |            |   |   |
| Net earned premiums                                                                    | 804             | 913 | 916 |
| Net investment income                                                                  | 52              | 61 | 60 |
| Other revenues                                                                         | (1)             | 0 | 0 |
| Total operating revenues                                                               | 855             | 974 | 976 |
| **Claims, Benefits and Expenses**                                                      |            |   |   |
| Net incurred claims and benefits                                                       | 479             | 488 | 489 |
| Policyholders' dividends                                                               | 0               | 0 | 0 |
| Amortization of deferred acquisition costs                                             | 168             | 204 | 223 |
| Other insurance related expenses                                                       | 138             | 151 | 140 |
| Other expenses                                                                         | 12              | 28 | 12 |
| Total claims, benefits and expenses                                                    | 797             | 871 | 864 |
| Operating income (loss) from continuing operations before income tax                   | 58              | 103 | 112 |
| Income tax (expense) benefit on operating income (loss)                                | (21)            | (34) | (43) |
| Net operating income (loss) from continuing operations                                 | 37              | 69 | 69 |
| Net realized investment gains (losses), pre-tax                                        | 1               | (1) | 5 |
| Income tax (expense) benefit on net realized investment gains (losses)                 | 0               | 1 | (2) |
| Net realized investment gains (losses), after tax                                      | 1               | 0 | 3 |
| Net income (loss) from continuing operations                                           | 38              | 69 | 72 |
| Life and Group Non-Core [Member]                                                       |            |   |   |
| **Segment Reporting Information [Line Items]**                                         |            |   |   |
| Net written premiums                                                                   | 542             | 553 | 552 |
| **Operating Revenues**                                                                 |            |   |   |
| Net earned premiums                                                                    | 548             | 556 | 559 |
| Net investment income                                                                  | 704             | 700 | 662 |
| Other revenues                                                                         | 7               | 16 | (4) |
| Total operating revenues                                                               | 1,259           | 1,272 | 1,217 |
| **Claims, Benefits and Expenses**                                                      |            |   |   |
| Net incurred claims and benefits                                                       | 1,421           | 1,304 | 1,261 |
| Policyholders' dividends                                                               | 0               | 0 | 0 |
| Amortization of deferred acquisition costs                                             | 314             | 28 | 28 |
| Other insurance related expenses                                                       | 142             | 130 | 130 |
| Other expenses                                                                         | 11              | 30 | 13 |
| Total claims, benefits and expenses                                                    | 1,888           | 1,492 | 1,432 |
| Operating income (loss) from continuing operations before income tax                   | (629)           | (220) | (215) |
| Income tax (expense) benefit on operating income (loss)                                | 315             | 151 | 141 |
| Net operating income (loss) from continuing operations                                 | (314)           | (69) | (74) |
| Net realized investment gains (losses), pre-tax                                        | (1)             | 7 | 26 |
| Income tax (expense) benefit on net realized investment gains (losses)                 | 9               | 0 | (8) |
| Net realized investment gains (losses), after tax                                      | 8               | 7 | 18 |
| Net income (loss) from continuing operations                                           | (306)           | (62) | (56) |
| Corporate and Other Non-Core [Member]                                                  |            |   |   |
| **Segment Reporting Information [Line Items]**                                         |            |   |   |
| Net written premiums                                                                   | 1               | 1 | (1) |
| **Operating Revenues**                                                                 |            |   |   |
| Net earned premiums                                                                    | 1               | 1 | (1) |
| Net investment income                                                                  | 17              | 23 | 32 |
| Other revenues                                                                         | 11              | 12 | 12 |
| Total operating revenues                                                               | 29              | 36 | 43 |
| **Claims, Benefits and Expenses**                                                      |            |   |   |
| Net incurred claims and benefits                                                       | 61              | (29) | 191 |
| Policyholders' dividends                                                               | 0               | 0 | 0 |
| Amortization of deferred acquisition costs                                             | 0               | 0 | 0 |
| Other insurance related expenses                                                       | (1)             | 1 | (3) |
| Other expenses                                                                         | 186             | 210 | 183 |
| Total claims, benefits and expenses                                                    | 246             | 182 | 371 |
| Operating income (loss) from continuing operations before income tax                   | (217)           | (146) | (328) |
| Income tax (expense) benefit on operating income (loss)                                | 80              | 54 | 118 |
| Net operating income (loss) from continuing operations                                 | (137)           | (92) | (210) |
| Net realized investment gains (losses), pre-tax                                        | 13              | 20 | 9 |
| Income tax (expense) benefit on net realized investment gains (losses)                 | (5)             | (8) | (3) |
| Net realized investment gains (losses), after tax                                      | 8               | 12 | 6 |
| Net income (loss) from continuing operations                                           | (129)           | (80) | (204) |
| Eliminations [Member]                                                                  |            |   |   |
| **Segment Reporting Information [Line Items]**                                         |            |   |   |
| Net written premiums                                                                   | (2)             | (2) | (2) |
| **Operating Revenues**                                                                 |            |   |   |
| Net earned premiums                                                                    | (2)             | (2) | (2) |
| Net investment income                                                                  | 0               | 0 | 0 |
| Other revenues                                                                         | (3)             | (5) | (2) |
| Total operating revenues                                                               | (5)             | (7) | (4) |
| **Claims, Benefits and Expenses**                                                      |            |   |   |
| Net incurred claims and benefits                                                       | 0               | 0 | 0 |
| Policyholders' dividends                                                               | 0               | 0 | 0 |
| Amortization of deferred acquisition costs                                             | 0               | 0 | 0 |
| Other insurance related expenses                                                       | (2)             | (2) | (2) |
| Other expenses                                                                         | (3)             | (5) | (2) |
| Total claims, benefits and expenses                                                    | (5)             | (7) | (4) |
| Operating income (loss) from continuing operations before income tax                   | 0               | 0 | 0 |
| Income tax (expense) benefit on operating income (loss)                                | 0               | 0 | 0 |
| Net operating income (loss) from continuing operations                                 | 0               | 0 | 0 |
| Net realized investment gains (losses), pre-tax                                        | 0               | 0 | 0 |
| Income tax (expense) benefit on net realized investment gains (losses)                 | 0               | 0 | 0 |
| Net realized investment gains (losses), after tax                                      | 0               | 0 | 0 |
| Net income (loss) from continuing operations                                           | $ 0             | $ 0 | $ 0 |

| X                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Income Tax Expense (Benefit) on Net Realized Investment Gains Losses
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Income Tax Expense (Benefit) on Operating Income (Loss)
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| - Definition
The income earned from investments in securities and property, equipment and other capital assets. It includes rent from property and equipment, dividends from shares in corporations, and interest from bonds, loans, mortgages, derivatives, commercial paper, bank accounts, certificates of deposits, treasuries, and other financial securities. It also includes realized gains and losses on trading securities.
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| - Definition
Net Operating Income (Loss) from Continuing Operations Attributable to Parent
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| - Definition
Net realized investment gains (losses)
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| - Definition
Operating Income (Loss) from Continuing Operations before Income Tax
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| - Definition
Operating Revenues
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| X                                                                                                                                                                                                                                                  |
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| - Definition
Other Insurance Related Expenses
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| - Definition
This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.
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| - Definition
The total amount of expense recognized during the period for future policy benefits, claims and claims adjustment costs, and for selling, general and administrative costs.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expense related to deferred policy acquisition costs.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.
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| - Definition
This element represents a sum total of expenses not separately reflected on the income statement for the period.
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| - Definition
Reflects the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement.
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| - Definition
Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred.
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| - Definition
Amount of expense for dividends to policyholders.
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| - Definition
Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned.
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| - Definition
Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums written.
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| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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