Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Tax Contingency [Line Items]
Net deferred tax benefit			$ (68.0)
Net income tax payments to US	$ 30.7	$ 34.3	42.7
P&C Insurance and Reinsurance (Ark/WM Outrigger) | Ark
Income Tax Contingency [Line Items]
Net deferred tax benefit			(51.0)
Financial Guarantee (HG Global) | HG Global
Income Tax Contingency [Line Items]
Net deferred tax benefit			$ (17.0)
Deferred tax liabilities		5.0
Deferred tax expense (benefit)		$ (5.0)
Domestic Tax Jurisdiction
Income Tax Contingency [Line Items]
Separate return limitation year operating loss carryforwards	8.2
Separate return limitation year internal revenue	0.6
Foreign Tax Jurisdiction
Income Tax Contingency [Line Items]
Tax credit carryforwards	3.7
Bermuda
Income Tax Contingency [Line Items]
Deferred tax liabilities	5.1
Deferred tax expense (benefit)	(5.1)
LUXEMBOURG
Income Tax Contingency [Line Items]
Deferred tax expense (benefit)	$ (78.1)