Insurance Liabilities - Discounting of Reserves (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Discounting of Reserves [Line Items]
U.S. workers' compensation	$ 2,111	$ 2,063
Retroactive reinsurance	(838)	(891)
Total reserve discount	1,273	1,172
Fortitude RE
Discounting of Reserves [Line Items]
Total reserve discount	$ 686	$ 693
Discount ceded on sale (as a percent)	100.00%	100.00%
United Kingdom
Discounting of Reserves [Line Items]
Total reserve discount	$ 162	$ 166