Investments - Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Net Investment Income [Line Items]
Total	$ 38.2	$ 34.3	$ 25.0
Investment expense	0.4	0.3	0.3
Net investment income	37.8	34.0	24.7
Interest on cash and cash equivalents
Net Investment Income [Line Items]
Total	8.2	8.3	4.2
Fixed maturities
Net Investment Income [Line Items]
Total	29.1	24.4	17.0
Short-term investments
Net Investment Income [Line Items]
Total	$ 0.9	$ 1.6	$ 3.8