Variable Interest Entities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Sep. 02, 2025	Dec. 31, 2024	Jul. 01, 2024	Jun. 30, 2024
Variable Interest Entity [Line Items]
Assets held-in-trust	$ 1,006.5		$ 950.1
Subsidiary - WM Outrigger Re | Preferred stocks
Variable Interest Entity [Line Items]
Basic ownership	100.00%		100.00%
Subsidiary - Distinguished Managing General Agent
Variable Interest Entity [Line Items]
Basic ownership	55.50%	55.50%
Bamboo CRV
Variable Interest Entity [Line Items]
Expected capital contribution	$ 10.0
BAM Surplus Notes | Surplus Notes
Variable Interest Entity [Line Items]
Interest rate				10.00%	8.20%
Subsidiary - HG Global
Variable Interest Entity [Line Items]
Purchase of surplus notes	$ 503.0
Subsidiary - HG Global | Maximum
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured	15.00%
Outrigger Re
Variable Interest Entity [Line Items]
Short-term investments, at fair value	$ 245.7		$ 203.7
Bamboo CRV | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Partnership interest, carrying value	$ 250.0
PassportCard/DavidShield | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Ownership interest	53.80%
Partnership interest, carrying value	$ 180.1
BroadStreet | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Ownership interest	10.90%
Partnership interest, carrying value	$ 160.0
Elementum | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Ownership interest	26.60%
Partnership interest, carrying value	$ 35.0
Limited Partnerships | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Partnership interest, carrying value	$ 251.2