Goodwill and other intangible assets Schedule of Goodwill (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Jan. 14, 2016	Dec. 31, 2015
Goodwill [Line Items]
Other Intangible Assets, Net	$ 6,991		$ 887
Goodwill [Roll Forward]
Goodwill, beginning of period	4,796
Goodwill, Acquired During Period	10,530
Goodwill, Translation Adjustments	155
Goodwill, end of period	15,481
North America Commercial P&C Insurance [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	1,203
Goodwill, Acquired During Period	5,711
Goodwill, Translation Adjustments	43
Goodwill, end of period	6,957
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	2,794
Goodwill, Translation Adjustments	98
Goodwill, end of period	4,970
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 [Line Items]
Increase Decrease on Acquired Unpaid Losses and Loss Expenses		$ 715
The Chubb Corporation [Member] | Minimum [Member]
Goodwill [Line Items]
Amortization Period of Increase Decrease to Acquired Unpaid Losses and Loss Expenses	5 years
The Chubb Corporation [Member] | Maximum [Member]
Goodwill [Line Items]
Amortization Period of Increase Decrease to Acquired Unpaid Losses and Loss Expenses	17 years