Statutory Capital and Surplus (Details) - USD ($)	Dec. 31, 2025	Dec. 31, 2024
Statutory Accounting Practices [Line Items]
Total investments	$ 8,323,900,000	$ 6,417,600,000
Assets held-in-trust	1,006,500,000	950,100,000
Lloyds Bank
Statutory Accounting Practices [Line Items]
Total investments	361,600,000	$ 361,500,000
P&C Insurance and Reinsurance (Ark/WM Outrigger) | WM Outrigger Re - Segment
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	231,800,000
Minimum regulatory capital requirement	$ 1
P&C Insurance and Reinsurance (Ark/WM Outrigger) | Ark
Statutory Accounting Practices [Line Items]
Percent of statutory capital balance	15.00%
Percent of statutory capital and surplus balance	25.00%
Maximum dividend payable	$ 425,100,000
Financial Guarantee (HG Global) | HG Global
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	731,700,000
Minimum regulatory capital requirement	1
Net unrestricted cash	3,900,000
Accrued interest	178,500,000
Ark
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	1,700,200,000
Minimum regulatory capital requirement	$ 578,100,000