Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	$ 4,729	$ 4,620	$ 13,473	$ 12,809
Net premiums earned	4,754	4,610	13,056	12,250
Net investment income	566	522	1,675	1,587
Net realized gains (losses) including OTTI	(120)	40	(297)	350
Losses and loss expenses	2,684	2,655	7,233	6,831
Policy benefits	125	138	383	379
Policy acquisition costs and administrative expenses	1,379	1,241	3,966	3,598
Interest (income) expense	70	72	213	205
Other (income) expense	(19)	(5)	(61)	22
Income tax expense (benefit)	176	155	402	392
Net income (loss)	785	916	2,298	2,760
Comprehensive income (loss)	298	1,030	2,754	1,247
ACE Limited (Parent Guarantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net investment income	1	1	2	2
Equity in earnings of subsidiaries	745	863	2,192	2,619
Net realized gains (losses) including OTTI	0	0	0	12
Policy acquisition costs and administrative expenses	18	13	57	40
Interest (income) expense	(7)	(8)	(26)	(23)
Other (income) expense	(54)	(62)	(146)	(157)
Income tax expense (benefit)	4	5	11	13
Net income (loss)	785	916	2,298	2,760
Comprehensive income (loss)	298	1,030	2,754	1,247
ACE INA Holdings Inc (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	0	0	0	0
Net premiums earned	0	0	0	0
Net investment income	0	0	1	2
Equity in earnings of subsidiaries	258	322	669	767
Net realized gains (losses) including OTTI	46	(2)	53	(2)
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	6	4	20	13
Interest (income) expense	68	69	209	200
Other (income) expense	2	6	22	21
Income tax expense (benefit)	(11)	(14)	(66)	(80)
Net income (loss)	239	255	538	613
Comprehensive income (loss)	33	339	810	(195)
Other ACE Limited Subsidiaries
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	4,729	4,620	13,473	12,809
Net premiums earned	4,754	4,610	13,056	12,250
Net investment income	565	521	1,672	1,583
Net realized gains (losses) including OTTI	(166)	42	(350)	340
Losses and loss expenses	2,684	2,655	7,233	6,831
Policy benefits	125	138	383	379
Policy acquisition costs and administrative expenses	1,355	1,224	3,889	3,545
Interest (income) expense	9	11	30	28
Other (income) expense	33	51	63	158
Income tax expense (benefit)	183	164	457	459
Net income (loss)	764	930	2,323	2,773
Comprehensive income (loss)	276	1,043	2,778	1,259
Consolidating Adjustments and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Equity in earnings of subsidiaries	(1,003)	(1,185)	(2,861)	(3,386)
Net income (loss)	(1,003)	(1,185)	(2,861)	(3,386)
Comprehensive income (loss)	$ (309)	$ (1,382)	$ (3,588)	$ (1,064)