Investments - Net Investment Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Gain (Loss) on Securities [Line Items]
Net investment losses	$ (13.0)	$ (17.3)	$ (24.0)
Fixed maturity securities
Gain (Loss) on Securities [Line Items]
Net investment losses	(6.6)	(21.1)	(20.3)
Equity securities
Gain (Loss) on Securities [Line Items]
Net investment losses	(1.4)	7.4	(3.9)
Short-term and other investments
Gain (Loss) on Securities [Line Items]
Net investment losses	$ (5.0)	$ (3.6)	$ 0.2