v3.26.1
RESERVE FOR LOSSES AND LOSS EXPENSES
 6 Months Ended
Jun. 30, 2026
Insurance [Abstract]  
RESERVE FOR LOSSES AND LOSS EXPENSES RESERVE FOR LOSSES AND LOSS EXPENSES
Reserve Roll-Forward

The following table presents a reconciliation of the Company's beginning and ending gross reserve for losses and loss expenses and net reserve for unpaid losses and loss expenses:
Six months ended June 30,
20262025
Gross reserve for losses and loss expenses, beginning of period$18,122,256 $17,218,929 
Less reinsurance recoverable on unpaid losses and loss expenses, beginning of period(8,951,763)(6,840,897)
Net reserve for unpaid losses and loss expenses, beginning of period9,170,493 10,378,032 
Net incurred losses and loss expenses related to:
Current year1,833,311 1,625,845 
Prior years(32,899)(38,166)
 1,800,412 1,587,679 
Net paid losses and loss expenses related to:
Current year(196,928)(166,553)
Prior years(1,233,370)(1,395,871)
 (1,430,298)(1,562,424)
Foreign exchange and other(61,837)291,481 
Ceded reserves related to retroactive transactions
185,620 (1,902,645)
123,783 (1,611,164)
Net reserve for unpaid losses and loss expenses, end of period9,664,390 8,792,123 
Reinsurance recoverable on unpaid losses and loss expenses, end of period8,949,022 9,086,900 
Gross reserve for losses and loss expenses, end of period$18,613,412 $17,879,023 

At June 30, 2026, net reserves for losses and loss expenses included estimated amounts for numerous catastrophe events. The magnitude and complexity of losses arising from certain of these events inherently increase the level of uncertainty and, therefore, the level of management judgment involved in arriving at estimated net reserves for losses and loss expenses. These events include U.S. winter storms and the Middle East Conflict in 2026, and the California Wildfires in 2025. As a result, actual losses for these events may ultimately differ materially from current estimates. During the six months ended June 30, 2026, the Company recognized catastrophe and weather-related losses, net of reinsurance, of $128 million (2025: $86 million).
Prior Year Reserve Development

The Company's net favorable (adverse) prior year reserve development arises from changes to estimates of losses and loss expenses related to loss events that occurred in previous calendar years. The following table presents net favorable (adverse) prior year reserve development by segment:
  Three months ended June 30,Six months ended June 30,
2026202520262025
Favorable (Adverse)Favorable (Adverse)Favorable (Adverse)Favorable (Adverse)
Insurance$11,852 $15,216 $26,911 $29,194 
Reinsurance2,984 5,013 5,988 8,972 
Total$14,836 $20,229 $32,899 $38,166 

The following sections provide further details on net favorable (adverse) prior year reserve development by segment and reserve class:

Insurance Segment:

Prior year reserve development by reserve class was as follows:
Three months ended June 30,Six months ended June 30,
2026202520262025
Favorable (Adverse)Favorable (Adverse)Favorable (Adverse)Favorable (Adverse)
Property
$7,902 $6,980 $17,842 $16,976 
Casualty
— — — — 
Specialty other
3,950 8,236 9,069 12,218 
Total$11,852 $15,216 $26,911 $29,194 
Reinsurance Segment:
Prior year reserve development by reserve class was as follows:
  Three months ended June 30,Six months ended June 30,
  2026202520262025
Favorable
(Adverse)		Favorable
(Adverse)		Favorable
(Adverse)		Favorable
(Adverse)
Casualty
$— $— $— $— 
Specialty
2,984 5,013 5,988 8,847 
Run-off
— — — 125 
Total$2,984 $5,013 $5,988 $8,972