Segment Information (Narrative) (Details) - segment	6 Months Ended
Jun. 30, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Number of reportable segments (in segments)	5
Number of operating segments	5
Workers' Compensation Insurance Segment
Segment Reporting Information [Line Items]
Worker's compensation SPC percentage ceded	100.00%
Syndicate 1729
Segment Reporting Information [Line Items]
Proportion of capital provided to support Lloyd's Syndicate 1729	5.00%	29.00%
Syndicate 6131
Segment Reporting Information [Line Items]
Proportion of capital provided to support Lloyd's Syndicate 1729	50.00%	100.00%

Alternative Market Solutions Percentage Ceded

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- Definition

This item represents the capital provided in support of a segment by a corporate member as a percentage of total capital provided by all members to support the segment.

+ References

No definition available.

+ Details

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8672-108599

+ Details

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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

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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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- Details

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