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Significant Transactions - Outrigger Re (Details) $ in Millions		1 Months Ended	3 Months Ended		12 Months Ended
	Dec. 20, 2022 USD ($) account	Jan. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2023 USD ($)
Outrigger Re
Other Significant Transactions [Line Items]
Ceded unearned premiums			$ 250.0		$ 250.0
Rollover amount			130.0
Short-term investments			$ 265.3	$ 203.7	265.3
Outrigger Re | Subsequent Event
Other Significant Transactions [Line Items]
Return of capital		$ 68.1
Outrigger Re
Other Significant Transactions [Line Items]
Business combination, consideration transferred				$ 205.0
Transaction costs					$ 1.3
Subsidiary - WM Outrigger Re | Preferred stocks
Other Significant Transactions [Line Items]
Basic ownership			100.00%	100.00%	100.00%
Redeemable Preferred Stock | Outrigger Re Ltd
Other Significant Transactions [Line Items]
Issuances of common shares	$ 250.0
Number of segregated accounts | account	4

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- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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