Investments - Offsetting of Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Asset derivatives
Net Amounts of Assets/ Liabilities Presented in the Consolidated Balance Sheets	$ 10.7	$ 16.8
Free-standing derivatives
Asset derivatives
Gross Amounts	10.7	16.8
Gross Amounts Offset in the Consolidated Balance Sheets	0.0	0.0
Net Amounts of Assets/ Liabilities Presented in the Consolidated Balance Sheets	10.7	16.8
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	4.5	13.7
Gross Amounts Not Offset in the Consolidated Balance Sheets, Cash Collateral Received	6.4	2.6
Net Amount	$ (0.2)	$ 0.5