| **Acquisition (Details) - Cincinnati Global $ in Millions**                               | Feb. 28, 2019 USD ($) |
|-------------------------------------------------------------------------------------------|-----------------------|
| **Assets**                                                                                |                  |
| Investments and other invested assets                                                     | $ 198                 |
| Cash and cash equivalents                                                                 | 64                    |
| Premiums receivable                                                                       | 45                    |
| Reinsurance recoverable                                                                   | 42                    |
| Other assets                                                                              | 23                    |
| Total assets acquired                                                                     | 372                   |
| **Liabilities**                                                                           |                  |
| Loss and loss expense reserves                                                            | 277                   |
| Unearned premiums                                                                         | 88                    |
| Other liabilities                                                                         | 24                    |
| Total liabilities assumed                                                                 | 389                   |
| **Fair value of identifiable intangible assets**                                          |                  |
| Syndicate capacity - indefinite lived                                                     | 31                    |
| Total fair value of identifiable intangible assets                                        | 50                    |
| Total purchase price paid                                                                 | 63                    |
| Total assets acquired (including fair value of identifiable intangible assets)            | 422                   |
| Fair value of net assets acquired prior to allocation of goodwill                         | 33                    |
| Excess of purchase price paid over fair value of net assets acquired assigned to goodwill | 30                    |
| Syndicate Broker Relationships                                                            |                  |
| **Fair value of identifiable intangible assets**                                          |                  |
| Definite lived intangible assets                                                          | 12                    |
| Value Of Business Acquired                                                                |                  |
| **Fair value of identifiable intangible assets**                                          |                  |
| Definite lived intangible assets                                                          | 4                     |
| Developed Technology Rights                                                               |                  |
| **Fair value of identifiable intangible assets**                                          |                  |
| Definite lived intangible assets                                                          | $ 3                   |

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Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.
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Amount due from customers or clients for goods or services, including trade receivables, that have been delivered or sold in the normal course of business, and amounts due from others, including related parties expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.
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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.
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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.
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