Investments - Additional Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026 USD ($) security	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($) security	Jun. 30, 2025 USD ($)	Dec. 31, 2025 USD ($)
Net Investment Income [Line Items]
Gross unrealized losses (less than for December 31, 2025)	$ 4.0		$ 4.0		$ 0.0
Pre-tax net realized capital gains (losses)	$ 0.2	$ (0.1)	$ 0.5	$ (0.1)
Number of debt securities held, unrealized loss position | security	541		541
Gross unrealized losses, twelve months or more	$ 0.0		$ 0.0		0.0
Financing receivable, allowance for credit loss	0.0		0.0
Restricted investments	82.5		82.5		81.5
Fixed Income Securities
Net Investment Income [Line Items]
Gross unrealized losses (less than for December 31, 2025)	$ 4.0		$ 4.0		0.1
Gross unrealized losses, twelve months or more					$ 0.1