Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Debt Instrument, Interest Reserve Account

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Investments Held In Trusts

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Investment Securities - Investments Held on Deposit or as Collateral (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022	Jun. 16, 2022
Debt and Equity Securities, FV-NI [Line Items]
Investments held in trusts	$ 524.0	$ 500.5
Assets held by insurance regulators	4.6	4.6
Other long-term investments	1,815.0	1,488.0
Outrigger Re \| Cash and Short Term Investments
Debt and Equity Securities, FV-NI [Line Items]
Investment owned, balance	211.4	203.7
Senior Notes \| Secured Debt
Debt and Equity Securities, FV-NI [Line Items]
Interest reserve account	29.7	31.2	$ 29.2
Lloyd’s trust deposits
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments	152.3	137.4
Additional Investments, Insurance Regulators and Reinsurance Counterparties \| Asset Pledged as Collateral
Debt and Equity Securities, FV-NI [Line Items]
Investments pledged as collateral	244.9	257.0
Short-term investments \| Asset Pledged as Collateral
Debt and Equity Securities, FV-NI [Line Items]
Investments pledged as collateral	145.5	90.3
Lloyds Bank
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	$ 335.3	$ 319.2