Goodwill, Other intangible assets, and Value of business acquired (Roll-forward of Goodwill by Business Segment) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)
Goodwill [Roll Forward]
Balance at beginning of period	$ 16,228
Foreign exchange revaluation and other	(53)
Balance at end of period	16,175
North America Commercial P&C Insurance [Member]
Goodwill [Roll Forward]
Balance at beginning of period	6,945
Foreign exchange revaluation and other	(9)
Balance at end of period	6,936
North America Personal P&C Insurance [Member]
Goodwill [Roll Forward]
Balance at beginning of period	2,230
Foreign exchange revaluation and other	(3)
Balance at end of period	2,227
North America Agricultural Insurance [Member]
Goodwill [Roll Forward]
Balance at beginning of period	134
Foreign exchange revaluation and other	0
Balance at end of period	134
Overseas General Insurance [Member]
Goodwill [Roll Forward]
Balance at beginning of period	4,605
Foreign exchange revaluation and other	(3)
Balance at end of period	4,602
Global Reinsurance [Member]
Goodwill [Roll Forward]
Balance at beginning of period	371
Foreign exchange revaluation and other	0
Balance at end of period	371
Segment Life [Member]
Goodwill [Roll Forward]
Balance at beginning of period	1,943
Foreign exchange revaluation and other	(38)
Balance at end of period	$ 1,905