Goodwill and other intangible assets Changes in Deferred Tax Liabilities due to Intangible Asset Amortization For the Next Five Years (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Changes in Deferred Tax Liabilities due to Intangible Asset Amortization [Line Items]
Decrease to Deferred Tax Liability Due to Intangible Amortization, Next Three to Six Months	$ (126)
Unearned Premium Reserves Amortization, Next Three Months	11,580	$ 8,552
The Chubb Corporation [Member]
Changes in Deferred Tax Liabilities due to Intangible Asset Amortization [Line Items]
Decrease to Deferred Tax Liability Due to Intangible Amortization, Next Three Months	(196)
Decrease to Deferred Tax Liability Due to Intangible Amortization, Next Six to Nine Months	(65)
Decrease to Deferred Tax Liability Due to Intangible Amortization, Next Twelve Months	(114)
Decrease to Deferred Tax Liability Due to Intangible Amortization, Year Two	(123)
Decrease to Deferred Tax Liability Due to Intangible Amortization, Year 3	(98)
Decrease to Deferred Tax Liability Due to Intangible Amortization, Year 4	(84)
Decrease to Deferred Tax Liability Due to Intangible Amortization, Year 5	(75)
Decrease to Deferred Tax Liability Due to Intangible Amortization, Total	(881)
Unearned Premium Reserves Amortization, Next Three Months	518
Unearned Premium Reserves Amortization, Next Three to Six Months	319
Unearned Premium Reserves Amortization, Next Six to Nine Months	143
Unearned Premium Reserves Amortization, Next Twelve Months	0
Unearned Premium Reserves Amortization, Year Two	0
Unearned Premium Reserves Amortization, Year Three	0
Unearned Premium Reserves Amortization, Year Four	0
Unearned Premium Reserves Amortization, Year Five	0
Unearned Premium Reserves Amortization, Total	$ 980