Income Taxes - Valuation Allowance (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Valuation Allowance [Line Items]
Valuation allowance	$ 89.2	$ 116.1
Financial Guarantee (HG Global) | BAM
Valuation Allowance [Line Items]
Increase (decrease) in valuation allowance	5.7	6.3
Net Operating Losses in Luxembourg Subsidiaries
Valuation Allowance [Line Items]
Valuation allowance	43.4	20.8
U S Losses and Other Federal Deferred Tax Benefits
Valuation Allowance [Line Items]
Valuation allowance	25.2	47.6
Net Operating Losses in Israel Subsidiaries
Valuation Allowance [Line Items]
Valuation allowance	20.6	46.9
Net Operating Losses in United Kingdom Subsidiaries
Valuation Allowance [Line Items]
Valuation allowance		0.8
Net Deferred Tax Assets For Certain U.S. Operations - Other Operations
Valuation Allowance [Line Items]
Increase (decrease) in valuation allowance	(8.6)	7.2
Net Deferred Tax Assets For BAM
Valuation Allowance [Line Items]
Increase (decrease) in valuation allowance	(3.1)	(8.7)
Investments Held in Luxembourg-Domiciled Subsidiaries
Valuation Allowance [Line Items]
Increase (decrease) in valuation allowance	4.2	31.6
Investments Held in Israel-Domiciled Subsidiaries
Valuation Allowance [Line Items]
Increase (decrease) in valuation allowance	$ 0.2	$ (0.4)