Investments - Net Investment Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Gain (Loss) on Securities [Line Items]
Net investment losses	$ (2.2)	$ (3.3)
Fixed maturity securities
Gain (Loss) on Securities [Line Items]
Net investment losses	0.5	0.2
Equity securities
Gain (Loss) on Securities [Line Items]
Net investment losses	(1.3)	(1.2)
Short-term investments and other
Gain (Loss) on Securities [Line Items]
Net investment losses	$ (1.4)	$ (2.3)