Intangible Assets (Roll-forward of Goodwill by Business Segment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Balance at beginning of period	$ 4,796	$ 4,904
Purchase price allocation adjustment		(4)
Foreign exchange revaluation and other	22	(300)
Balance at end of period	15,332	4,796
North America Commercial P&C Insurance
Goodwill [Roll Forward]
Balance at beginning of period	1,203	1,211
Foreign exchange revaluation and other	44	(8)
Balance at end of period	6,961	1,203
North American Personal P&C [Member]
Goodwill [Roll Forward]
Balance at beginning of period	196	0
Purchase price allocation adjustment		0
Foreign exchange revaluation and other	14	0
Balance at end of period	2,235	196
North America Agricultural Insurance
Goodwill [Roll Forward]
Balance at beginning of period	134	134
Foreign exchange revaluation and other	0	0
Balance at end of period	134	134
Overseas General Insurance
Goodwill [Roll Forward]
Balance at beginning of period	2,078	2,366
Foreign exchange revaluation and other	(36)	(284)
Balance at end of period	4,817	2,078
Global Reinsurance
Goodwill [Roll Forward]
Balance at beginning of period	365	365
Foreign exchange revaluation and other	0	0
Balance at end of period	365	365
Life Insurance
Goodwill [Roll Forward]
Balance at beginning of period	820	828
Foreign exchange revaluation and other	0	(8)
Balance at end of period	820	820
Fianzas Monterrey | North America Commercial P&C Insurance
Goodwill [Roll Forward]
Purchase price allocation adjustment		0
Fianzas Monterrey | North America Agricultural Insurance
Goodwill [Roll Forward]
Purchase price allocation adjustment		0
Fianzas Monterrey | Overseas General Insurance
Goodwill [Roll Forward]
Purchase price allocation adjustment		(4)
Fianzas Monterrey | Global Reinsurance
Goodwill [Roll Forward]
Purchase price allocation adjustment		0
Fianzas Monterrey | Life Insurance
Goodwill [Roll Forward]
Purchase price allocation adjustment		0
Fireman's Fund high net worth personal lines [Member]
Goodwill [Roll Forward]
Acquisition		196
Fireman's Fund high net worth personal lines [Member] | North America Commercial P&C Insurance
Goodwill [Roll Forward]
Acquisition		0
Fireman's Fund high net worth personal lines [Member] | North American Personal P&C [Member]
Goodwill [Roll Forward]
Acquisition		196
Fireman's Fund high net worth personal lines [Member] | North America Agricultural Insurance
Goodwill [Roll Forward]
Acquisition		0
Fireman's Fund high net worth personal lines [Member] | Overseas General Insurance
Goodwill [Roll Forward]
Acquisition		0
Fireman's Fund high net worth personal lines [Member] | Global Reinsurance
Goodwill [Roll Forward]
Acquisition		0
Fireman's Fund high net worth personal lines [Member] | Life Insurance
Goodwill [Roll Forward]
Acquisition		$ 0
The Chubb Corporation [Member]
Goodwill [Roll Forward]
Acquisition	10,514
The Chubb Corporation [Member] | North America Commercial P&C Insurance
Goodwill [Roll Forward]
Acquisition	5,714
The Chubb Corporation [Member] | North American Personal P&C [Member]
Goodwill [Roll Forward]
Acquisition	2,025
The Chubb Corporation [Member] | North America Agricultural Insurance
Goodwill [Roll Forward]
Acquisition	0
The Chubb Corporation [Member] | Overseas General Insurance
Goodwill [Roll Forward]
Acquisition	2,775
The Chubb Corporation [Member] | Global Reinsurance
Goodwill [Roll Forward]
Acquisition	0
The Chubb Corporation [Member] | Life Insurance
Goodwill [Roll Forward]
Acquisition	$ 0