Investments - Offsetting of Assets and Liabilities (Details) - Free-standing derivatives - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Asset derivatives:
Gross Amounts	$ 13.8	$ 18.5
Gross Amounts Offset in the Consolidated Balance Sheets	0.0	0.0
Net Amounts of Assets/ Liabilities Presented in the Consolidated Balance Sheets	13.8	18.5
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	0.0	0.0
Gross Amounts Not Offset in the Consolidated Balance Sheets, Cash Collateral Received	14.4	20.4
Net Amount	$ (0.6)	$ (1.9)