Reserve for Property and Casualty Insurance Claims and Claims Expense - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Increase (decrease) in claims and claims expense
Losses from catastrophes, net of recoveries	$ 2,900	$ 2,800	$ 2,650
Catastrophe
Increase (decrease) in claims and claims expense
Losses from catastrophes, net of recoveries	4,960	$ 5,640	$ 3,110
Catastrophe claims, pre-tax loss before reinsurance, threshold	$ 1