Claim and Claim Adjustment Expense Reserves - Net Prior Year Loss Reserve Development in Property and Casualty Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Net Prior Year Development [Abstract]
Pretax favorable development	$ 12	$ 15
Medical professional liability
Net Prior Year Development [Abstract]
Pretax favorable development	8	8
Surety
Net Prior Year Development [Abstract]
Pretax favorable development	(9)	(15)
Workers’ compensation
Net Prior Year Development [Abstract]
Pretax favorable development	(2)
Property and other
Net Prior Year Development [Abstract]
Pretax favorable development	$ (9)	$ (8)