Fair Value Measurements - Fair Value Hierarchy for Financial Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Financial Assets:
Fixed maturities	$ 607.4	$ 627.4
Short term investments	27.5	45.8
Total	634.9	673.2
Financial Liabilities:
Fair value of public and private warrant liabilities (less than)	0.1	0.1
Corporate debt securities
Financial Assets:
Fixed maturities	470.8	449.9
U.S. Government obligations
Financial Assets:
Fixed maturities	107.7	175.9
Asset-backed securities
Financial Assets:
Fixed maturities	22.9	1.6
Non-U.S. government obligations
Financial Assets:
Fixed maturities	6.0	0.0
Warrant liability
Financial Liabilities:
Warrant liability	0.0	0.0
Level 1
Financial Assets:
Fixed maturities	0.0	0.0
Short term investments	0.0	0.0
Total	0.0	0.0
Level 1 | Corporate debt securities
Financial Assets:
Fixed maturities	0.0	0.0
Level 1 | U.S. Government obligations
Financial Assets:
Fixed maturities	0.0	0.0
Level 1 | Asset-backed securities
Financial Assets:
Fixed maturities	0.0	0.0
Level 1 | Non-U.S. government obligations
Financial Assets:
Fixed maturities	0.0	0.0
Level 1 | Warrant liability
Financial Liabilities:
Warrant liability	0.0	0.0
Level 2
Financial Assets:
Fixed maturities	607.4	627.4
Short term investments	27.5	45.8
Total	634.9	673.2
Level 2 | Corporate debt securities
Financial Assets:
Fixed maturities	470.8	449.9
Level 2 | U.S. Government obligations
Financial Assets:
Fixed maturities	107.7	175.9
Level 2 | Asset-backed securities
Financial Assets:
Fixed maturities	22.9	1.6
Level 2 | Non-U.S. government obligations
Financial Assets:
Fixed maturities	6.0	0.0
Level 2 | Warrant liability
Financial Liabilities:
Warrant liability	0.0	0.0
Level 3
Financial Assets:
Fixed maturities	0.0	0.0
Short term investments	0.0	0.0
Total	0.0	0.0
Level 3 | Corporate debt securities
Financial Assets:
Fixed maturities	0.0	0.0
Level 3 | U.S. Government obligations
Financial Assets:
Fixed maturities	0.0	0.0
Level 3 | Asset-backed securities
Financial Assets:
Fixed maturities	0.0	0.0
Level 3 | Non-U.S. government obligations
Financial Assets:
Fixed maturities	0.0	0.0
Level 3 | Warrant liability
Financial Liabilities:
Warrant liability	$ 0.0	$ 0.0