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, 2024
Property and Accident & Health
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	23.80%
2	32.80%
3	18.30%
4	6.40%
5	2.80%
6	1.30%
7	0.50%
8	0.80%
9	0.10%
10	0.10%
Specialty
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	19.30%
2	30.80%
3	10.90%
4	4.90%
5	7.30%
6	2.50%
7	1.50%
8	1.80%
9	1.30%
10	(1.10%)
Marine & Energy
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	12.90%
2	30.50%
3	19.50%
4	8.00%
5	4.90%
6	6.90%
7	0.30%
8	0.40%
9	0.30%
10	0.10%
Casualty-Active
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	4.40%
2	8.40%
3	11.60%
4	14.40%
5	9.50%
6	11.70%
7	6.30%
8	4.80%
9	3.70%
10	3.10%
Casualty-Runoff
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	8.80%
2	14.10%
3	15.60%
4	14.80%
5	8.50%
6	6.80%
7	5.90%
8	4.10%
9	3.10%
10	2.00%