Investments - Schedule of Commercial Mortgage and Private Loans (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cost	$ 787.4	$ 144.8
Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cost	210.1	144.8
Private Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cost	577.3	0.0
Fair Value
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cost	811.4	148.8
Fair Value | Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cost	214.2	148.8
Fair Value | Private Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cost	$ 597.2	$ 0.0