Loss and Loss Adjustment Expense Reserves - Average Annual Percentage Payout of Incurred Losses and Allocated LAE by Age, Net of Reinsurance (Details) - P&C Insurance and Reinsurance (Ark/WM Outrigger)	Dec. 31, 2025
Property and Accident & Health
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	27.40%
2	31.90%
3	18.40%
4	6.40%
5	2.90%
6	1.90%
7	0.40%
8	0.90%
9	0.20%
10	0.10%
Specialty
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	18.20%
2	26.80%
3	13.20%
4	8.70%
5	6.30%
6	2.50%
7	2.10%
8	1.80%
9	1.20%
10	1.00%
Marine & Energy
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	12.10%
2	27.10%
3	17.30%
4	12.10%
5	6.40%
6	6.50%
7	0.50%
8	0.40%
9	0.10%
10	0.10%
Casualty-Active
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	3.80%
2	7.50%
3	11.40%
4	12.90%
5	10.00%
6	11.20%
7	7.20%
8	5.10%
9	4.20%
10	3.40%
Casualty-Runoff
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	8.80%
2	13.90%
3	15.30%
4	14.80%
5	8.50%
6	6.70%
7	5.90%
8	4.20%
9	3.20%
10	2.20%