Goodwill and Value of business acquired (Roll-forward of Goodwill by Business Segment) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2023 USD ($)
Goodwill [Roll Forward]
Balance at beginning of period	$ 16,228
Foreign exchange revaluation and other	94
Balance at end of period	16,322
North America Commercial P&C Insurance [Member]
Goodwill [Roll Forward]
Balance at beginning of period	6,945
Foreign exchange revaluation and other	10
Balance at end of period	6,955
North America Personal P&C Insurance [Member]
Goodwill [Roll Forward]
Balance at beginning of period	2,230
Foreign exchange revaluation and other	4
Balance at end of period	2,234
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	139
Balance at end of period	4,744
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	(59)
Balance at end of period	$ 1,884