Reinsurance - Schedule of premiums written, earned and policy fees (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Premiums earned:
Premiums	$ 31,857	$ 31,259	$ 28,523
Policy Fees
Net	2,972	3,051	2,917
Short-Duration Insurance
Premiums written:
Direct	32,025	30,910	28,521
Assumed	7,385	7,209	5,947
Ceded	(12,650)	(11,702)	(11,012)
Net	26,760	26,417	23,456
Premiums earned:
Direct	32,053	30,279	28,596
Assumed	7,137	6,640	5,984
Ceded	(12,425)	(11,301)	(10,435)
Premiums	26,765	25,618	24,145
Long-Duration Insurance
Premiums written:
Direct	4,738	4,596	4,381
Assumed	1,318	2,265	1,058
Ceded	(964)	(1,220)	(1,061)
Net	5,092	5,641	4,378
Policy Fees
Direct	3,048	3,130	2,957
Assumed	0	0	0
Ceded	(76)	(79)	(40)
Net	$ 2,972	$ 3,051	$ 2,917