Investments - Contractual Maturities of Bonds (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Cost or Amortized Cost
Due in one year or less	$ 100.8
Due after one year through five years	589.1
Due after five years through ten years	0.0
Due after ten years	0.0
Sub-total	689.9
Asset-backed securities and collateralized loan obligations	82.5
Cost or Amortized Cost	772.4	$ 706.0
Fair Value
Due in one year or less	100.9
Due after one year through five years	585.4
Due after five years through ten years	0.0
Due after ten years	0.0
Sub-total	686.3
Asset-backed securities and collateralized loan obligations	82.2
Total	$ 768.5	$ 708.8