Schedule IV (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct	$ 31,463	$ 31,208	$ 30,781
Ceded Premiums Earned	11,459	11,618	12,267
Assumed	3,747	3,947	7,050
Premiums	$ 23,751	$ 23,537	$ 25,564
Percent of Amount Assumed to Net	15.80%	16.80%	27.60%
Accident and health
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct	$ 2,535	$ 2,507	$ 2,612
Ceded Premiums Earned	108	104	107
Assumed	35	30	35
Premiums	$ 2,462	$ 2,433	$ 2,540
Percent of Amount Assumed to Net	1.40%	1.20%	1.40%
Property and liability
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct	$ 28,928	$ 28,701	$ 28,169
Ceded Premiums Earned	11,351	11,514	12,160
Assumed	3,712	3,917	7,015
Premiums	$ 21,289	$ 21,104	$ 23,024
Percent of Amount Assumed to Net	17.40%	18.60%	30.50%