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, 2013	Sep. 30, 2012		Sep. 30, 2013	Sep. 30, 2012
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	$ 4,620	$ 4,716		$ 12,809	$ 12,418
Net premiums earned	4,610	4,665		12,250	11,829
Net investment income	522	533		1,587	1,614
Net realized gains (losses) including OTTI	40	(60)		350	(194)
Losses and loss expenses	2,655	3,047		6,831	6,970
Policy benefits	138	130		379	379
Policy acquisition costs and administrative expenses	1,241	1,128		3,598	3,353
Interest (income) expense	72	63		205	187
Other (income) expense	(5)	(17)		22	14
Income tax expense (benefit)	155	147		392	405
Net income (loss)	916	640		2,760	1,941
Comprehensive income (loss)	1,030	1,316		1,247	3,044
Parent Company [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net investment income	1	0		2	1
Equity in earnings of subsidiaries	863	616		2,619	1,845
Net realized gains (losses) including OTTI	0	(4)		12	18
Policy acquisition costs and administrative expenses	13	16		40	42
Interest (income) expense	(8)	(8)		(23)	(25)
Other (income) expense	(62)	(39)		(157)	(102)
Income tax expense (benefit)	5	3		13	8
Net income (loss)	916	640		2,760	1,941
Comprehensive income (loss)	1,030	1,316		1,247	3,044
Guarantor Subsidiaries [Member]
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	1		2	2
Equity in earnings of subsidiaries	322	285		767	775
Net realized gains (losses) including OTTI	(2)	0		(2)	0
Losses and loss expenses	0	0		0	0
Policy benefits	0	0		0	0
Policy acquisition costs and administrative expenses	4	6		13	20
Interest (income) expense	69	60		200	175
Other (income) expense	6	7		21	(8)
Income tax expense (benefit)	(14)	(24)		(80)	(72)
Net income (loss)	255	237		613	662
Comprehensive income (loss)	339	593		(195)	1,203
Other Ace Limited Subsidiaries And Eliminations [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	4,620	4,716		12,809	12,418
Net premiums earned	4,610	4,665		12,250	11,829
Net investment income	521	532		1,583	1,611
Net realized gains (losses) including OTTI	42	(56)		340	(212)
Losses and loss expenses	2,655	3,047		6,831	6,970
Policy benefits	138	130		379	379
Policy acquisition costs and administrative expenses	1,224	1,106		3,545	3,291
Interest (income) expense	11	11		28	37
Other (income) expense	51	15		158	124
Income tax expense (benefit)	164	168		459	469
Net income (loss)	930	664		2,773	1,958
Comprehensive income (loss)	1,043	1,339		1,259	3,060
Consolidation, Eliminations [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Equity in earnings of subsidiaries	(1,185)	(901)		(3,386)	(2,620)
Net income (loss)	(1,185)	(901)		(3,386)	(2,620)
Comprehensive income (loss)	(1,382)	(1,932)		(1,064)	(4,263)
Scenario, Previously Reported [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written		4,716			12,418
Net premiums earned		4,665			11,829
Net investment income		533			1,614
Net realized gains (losses) including OTTI		(60)			(194)
Losses and loss expenses		3,047			6,970
Policy benefits		130			379
Policy acquisition costs and administrative expenses		1,128			3,353
Interest (income) expense		(63)			(187)
Other (income) expense		17			(14)
Income tax expense (benefit)		147			405
Net income (loss)		640			1,941
Comprehensive income (loss)		1,316			3,044
Scenario, Previously Reported [Member] | Parent Company [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net investment income		0			1
Equity in earnings of subsidiaries		616			1,845
Net realized gains (losses) including OTTI		(4)			18
Policy acquisition costs and administrative expenses		16			42
Interest (income) expense		8			25
Other (income) expense		39			102
Income tax expense (benefit)		3			8
Net income (loss)		640			1,941
Comprehensive income (loss)		1,316			3,044
Scenario, Previously Reported [Member] | Guarantor Subsidiaries [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written		2,868			7,293
Net premiums earned		2,819			6,967
Net investment income		255			777
Equity in earnings of subsidiaries		0			0
Net realized gains (losses) including OTTI		11			71
Losses and loss expenses		1,977			4,484
Policy benefits		77			217
Policy acquisition costs and administrative expenses		587			1,883
Interest (income) expense		(67)			(191)
Other (income) expense		(17)			(51)
Income tax expense (benefit)		123			327
Net income (loss)		237			662
Comprehensive income (loss)		593			1,203
Scenario, Previously Reported [Member] | Other Ace Limited Subsidiaries And Eliminations [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written		1,848	[1]		5,125	[1]
Net premiums earned		1,846	[1]		4,862	[1]
Net investment income		278	[1]		836	[1]
Net realized gains (losses) including OTTI		(67)	[1]		(283)	[1]
Losses and loss expenses		1,070	[1]		2,486	[1]
Policy benefits		53	[1]		162	[1]
Policy acquisition costs and administrative expenses		525	[1]		1,428	[1]
Interest (income) expense		(4)	[1]		(21)	[1]
Other (income) expense		(5)	[1]		(65)	[1]
Income tax expense (benefit)		21	[1]		70	[1]
Net income (loss)		379	[1]		1,183	[1]
Comprehensive income (loss)		23	[1]		642	[1]
Scenario, Previously Reported [Member] | Consolidation, Eliminations [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Equity in earnings of subsidiaries		(616)	[2]		(1,845)	[2]
Net income (loss)		(616)	[2]		(1,845)	[2]
Comprehensive income (loss)		$ (616)	[2]		$ (1,845)	[2]

[1] Includes all other subsidiaries of ACE Limited and intercompany eliminations.

[2] Includes ACE Limited parent company eliminations.