Investment Securities - Lloyd's Trust Deposits, Bank Loan Fund, and Insurance-Linked Securities Funds (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Investments held in trusts	$ 455.1	$ 479.5
Hedge funds | Minimum
Debt and Equity Securities, FV-NI [Line Items]
Redemptions and advanced redemption notice period	45 days
Hedge funds | Maximum
Debt and Equity Securities, FV-NI [Line Items]
Redemptions and advanced redemption notice period	90 days
Bank loan fund
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	$ 155.7
Lloyds Bank
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	311.4	$ 342.8
Investments held in trusts	117.8
ILS funds
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	$ 49.4
ILS funds | Minimum
Debt and Equity Securities, FV-NI [Line Items]
Redemptions and advanced redemption notice period	30 days
ILS funds | Maximum
Debt and Equity Securities, FV-NI [Line Items]
Redemptions and advanced redemption notice period	90 days