CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
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)	2,565,733	2,560,452
Common shares, outstanding shares (in shares)	2,565,733	2,560,452
P&C Insurance and Reinsurance (Ark/WM Outrigger) | Operating Segments
Restricted cash	$ 24.7	$ 0.7
P&C Insurance Distribution (Bamboo) | Operating Segments
Restricted cash	$ 58.3	$ 0.0