Investment Securities - Lloyd's Trust Deposits, Bank Loan Fund, and Insurance-Linked Securities Funds (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Investments held in trusts	$ 463.7	$ 479.5
Minimum
Debt and Equity Securities, FV-NI [Line Items]
Redemptions and advanced redemption notice period	30 days
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	$ 162.4
Lloyds Bank
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	305.6	$ 342.8
Investments held in trusts	113.2
ILS funds
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	$ 51.7