Goodwill and other intangible assets Goodwill Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Jan. 14, 2016	Dec. 31, 2015
Goodwill [Line Items]
Other Intangible Assets, Net	$ 8,000		$ 887
Goodwill [Roll Forward]
Goodwill, beginning of period	4,796
Goodwill, Acquired During Period	10,445
Goodwill, Translation Adjustments	163
Goodwill, end of period	15,404
North America Commercial P&C Insurance [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	1,203
Goodwill, Acquired During Period	5,667
Goodwill, Translation Adjustments	40
Goodwill, end of period	6,910
North America Personal P&C Insurance [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	196
Goodwill, Acquired During Period	2,025
Goodwill, Translation Adjustments	13
Goodwill, end of period	2,234
North America Agricultural Insurance [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	134
Goodwill, Acquired During Period	0
Goodwill, Translation Adjustments	0
Goodwill, end of period	134
Overseas General Insurance [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	2,078
Goodwill, Acquired During Period	2,753
Goodwill, Translation Adjustments	109
Goodwill, end of period	4,940
Global Reinsurance [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	365
Goodwill, Acquired During Period	0
Goodwill, Translation Adjustments	0
Goodwill, end of period	365
Life Insurance [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	820
Goodwill, Acquired During Period	0
Goodwill, Translation Adjustments	1
Goodwill, end of period	821
The Chubb Corporation [Member]
Goodwill [Roll Forward]
Deferred Tax Liabilities, Intangible Assets	$ 2,465	$ 2,679
Increase Decrease on Acquired Unpaid Losses and Loss Expenses		$ 715
The Chubb Corporation [Member] | Minimum [Member]
Goodwill [Roll Forward]
Amortization Period of Increase Decrease to Acquired Unpaid Losses and Loss Expenses	5 years
The Chubb Corporation [Member] | Maximum [Member]
Goodwill [Roll Forward]
Amortization Period of Increase Decrease to Acquired Unpaid Losses and Loss Expenses	17 years