Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	$ 4,343		$ 3,295		$ 11,742		$ 10,286
Net premiums earned	4,490		3,422		11,556		9,932
Net investment income	564		516		1,677		1,538
Net realized gains (losses) including OTTI	(760)		(50)		(878)		127
Losses and loss expenses	2,745		1,887		7,234		5,608
Policy benefits	83		93		282		267
Policy acquisition costs and administrative expenses	1,183		1,040		3,351		3,053
Interest expense	62		58		187		162
Other (income) expense	87		(25)		82		(26)
Income tax expense	165		160		384		426
Net income (loss)	(31)		675		835		2,107
ACE Limited (Parent Guarantor) [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net investment income					1
Equity in earnings of subsidiaries	(55)		653		772		2,036
Net realized gains (losses) including OTTI	2		(8)				3
Policy acquisition costs and administrative expenses	14		16		50		48
Interest expense	(9)		(9)		(27)		(28)
Other (income) expense	(30)		(40)		(92)		(94)
Income tax expense	3		3		7		6
Net income (loss)	(31)		675		835		2,107
ACE INA Holdings Inc. (Subsidiary Issuer) [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	2,581		1,965		6,910		6,185
Net premiums earned	2,700		2,031		6,863		5,881
Net investment income	281		253		825		760
Net realized gains (losses) including OTTI	28		(13)		32		60
Losses and loss expenses	1,782		1,202		4,521		3,665
Policy benefits	22		46		121		112
Policy acquisition costs and administrative expenses	625		586		1,813		1,730
Interest expense	66		63		199		184
Other (income) expense	83		14		115		52
Income tax expense	146		126		325		329
Net income (loss)	285		234		626		629
Other ACE Limited Subsidiaries And Eliminations [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	1,762	[1]	1,330	[1]	4,832	[1]	4,101	[1]
Net premiums earned	1,790	[1]	1,391	[1]	4,693	[1]	4,051	[1]
Net investment income	283	[1]	263	[1]	851	[1]	778	[1]
Net realized gains (losses) including OTTI	(790)	[1]	(29)	[1]	(910)	[1]	64	[1]
Losses and loss expenses	963	[1]	685	[1]	2,713	[1]	1,943	[1]
Policy benefits	61	[1]	47	[1]	161	[1]	155	[1]
Policy acquisition costs and administrative expenses	556	[1]	448	[1]	1,521	[1]	1,302	[1]
Interest expense	(5)	[1]	(5)	[1]	(13)	[1]	(22)	[1]
Other (income) expense	34	[1]	1	[1]	59	[1]	16	[1]
Income tax expense	16	[1]	31	[1]	52	[1]	91	[1]
Net income (loss)	(342)	[1]	418	[1]	141	[1]	1,408	[1]
Consolidating Adjustments [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Equity in earnings of subsidiaries	55	[2]	(653)	[2]	(772)	[2]	(2,036)	[2]
Policy acquisition costs and administrative expenses	(12)	[2]	(10)	[2]	(33)	[2]	(27)	[2]
Interest expense	10	[2]	9	[2]	28	[2]	28	[2]
Net income (loss)	$ 57	[2]	$ (652)	[2]	$ (767)	[2]	$ (2,037)	[2]

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

[2] Includes ACE Limited parent company eliminations.