Summary of significant accounting policies (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of significant accounting policies [Line Items]
Deferred Marketing Costs, Amortization Period	10 years
Deferred marketing costs reported in Deferred policy acquisition costs	$ 307	$ 274
Amortization expense for deferred marketing costs	128	119	128
Recoverable from unrated reinsurers, ceded reserve, default factor (percent)	34.00%
Reinsurance business assumed	27	32
Percentage of fair value of loaned securities	102.00%
Maximum overdraft balance guaranteed by ACE Ltd	300
Quality assessment threshold used in goodwill impairment testing	50.00%
Supplemental Information for Property, Casualty Insurance Underwriters, Reserves for Unpaid Claims and Claims Adjustment Expense	26,831	26,547	25,875
Gross liability for the amounts due to claimants	631
Reinsurance recoverables for amounts due from life insurance companies	577
Deposit assets reflected in Other assets	100	138
Reinsurance deposit liabilities included in Deposit liabilities	131	283
Contract holder deposit funds included in Deposit liabilities	699	548
Net operating results of ESIS included within Administrative expenses	25	23	21
Structured settlements
Summary of significant accounting policies [Line Items]
Loss and loss expenses reserves, net of discount	$ 54	$ 58
Minimum
Summary of significant accounting policies [Line Items]
Amortization period for value of reinsurance business assumed	9 years
Finite-lived intangible asset useful life	1 year
Interest rates used in calculating reserves	1.00%	1.00%
Reinsurance Premiums, Amortization Period	1 year
Maximum
Summary of significant accounting policies [Line Items]
Amortization period for value of reinsurance business assumed	40 years
Finite-lived intangible asset useful life	20 years
Interest rates used in calculating reserves	6.50%	4.50%
Reinsurance Premiums, Amortization Period	3 years