CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Common shares, par value per share (in dollars per share)	$ 1	$ 1
Common shares, authorized shares (in shares)	50,000,000	50,000,000
Common shares, issued shares (in shares)	2,575,161	2,568,148
Common shares, outstanding shares (in shares)	2,575,161	2,568,148
P&C Insurance and Reinsurance (Ark/WM Outrigger) | Operating Segments
Restricted cash	$ 8.0	$ 14.1
Specialty Insurance Distribution (Distinguished) | Operating Segments
Restricted cash	$ 0.4	$ 0.0