Reinsurance - Schedule of Short-Duration Insurance Premiums Written and Earned (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Premiums earned:
Direct	$ 31,208	$ 30,781	$ 32,053
Assumed	3,947	7,050	7,137
Ceded	(11,618)	(12,267)	(12,425)
Net	23,537	25,564	26,765
Short-Duration Insurance
Premiums written:
Direct	31,743	31,445	32,025
Assumed	3,950	7,951	7,385
Ceded	(11,791)	(12,190)	(12,650)
Net	23,902	27,206	26,760
Premiums earned:
Direct	31,208	30,781	32,053
Assumed	3,947	7,050	7,137
Ceded	(11,618)	(12,267)	(12,425)
Net	$ 23,537	$ 25,564	$ 26,765
Percent of amount assumed to net	16.80%	27.60%	26.70%