Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011		Dec. 31, 2010
Condensed Financial Statements Captions [Line Items]
Investments	$ 56,792		$ 55,676
Cash	715		614		1,115	[1]	772	[1]
Insurance and reinsurance balances receivable	4,487		4,387
Reinsurance recoverable on losses and loss expenses	12,057		12,389
Reinsurance recoverable on policy benefits	243		249
Value of business acquired	669		676
Goodwill and other intangible assets	4,860		4,799
Other assets	9,926		8,531
Total assets	89,749		87,321
Unpaid losses and loss expenses	37,247		37,477
Unearned premiums	6,664		6,334
Future policy benefits	4,358		4,274
Short-term debt	1,531		1,251
Long-term debt	3,360		3,360
Trust preferred securities	309		309
Other liabilities	10,849		9,984
Total liabilities	64,318		62,989
Total shareholders' equity	25,431		24,332		23,228
Total liabilities and shareholders' equity	89,749		87,321
Parent guarantor ownership percentage of subsidiary issuer	100.00%		100.00%
ACE Limited (Parent Guarantor) [Member]
Condensed Financial Statements Captions [Line Items]
Investments	34		33
Cash	162		106		354	[1]	308	[1]
Investments in subsidiaries	25,197		23,871
Due from subsidiaries and affiliates, net	376		498
Other assets	15		8
Total assets	25,784		24,516
Short-term debt	130
Other liabilities	223		184
Total liabilities	353		184
Total shareholders' equity	25,431		24,332
Total liabilities and shareholders' equity	25,784		24,516
ACE INA Holdings Inc. (Subsidiary Issuer) [Member]
Condensed Financial Statements Captions [Line Items]
Investments	29,078		28,848
Cash	496		382		980	[1]	573	[1]
Insurance and reinsurance balances receivable	4,050		3,944
Reinsurance recoverable on losses and loss expenses	16,685		17,146
Reinsurance recoverable on policy benefits	1,140		941
Value of business acquired	669		676
Goodwill and other intangible assets	4,306		4,248
Other assets	7,683		7,018
Total assets	64,107		63,203
Unpaid losses and loss expenses	30,691		30,837
Unearned premiums	5,726		5,416
Future policy benefits	3,766		3,673
Due to subsidiaries and affiliates, net	281		316
Short-term debt	851		850
Long-term debt	3,360		3,360
Trust preferred securities	309		309
Other liabilities	8,233		7,769
Total liabilities	53,217		52,530
Total shareholders' equity	10,890		10,673
Total liabilities and shareholders' equity	64,107		63,203
Other ACE Limited Subsidiaries And Eliminations [Member]
Condensed Financial Statements Captions [Line Items]
Investments	27,680	[2]	26,795	[2]
Cash	57	[2]	126	[2]	(219)	[1],[2]	(109)	[1],[2]
Insurance and reinsurance balances receivable	437	[2]	443	[2]
Reinsurance recoverable on losses and loss expenses	(4,628)	[2]	(4,757)	[2]
Reinsurance recoverable on policy benefits	(897)	[2]	(692)	[2]
Goodwill and other intangible assets	554	[2]	551	[2]
Other assets	2,228	[2]	1,505	[2]
Total assets	25,431	[2]	23,971	[2]
Unpaid losses and loss expenses	6,556	[2]	6,640	[2]
Unearned premiums	938	[2]	918	[2]
Future policy benefits	592	[2]	601	[2]
Due to subsidiaries and affiliates, net	95	[2]	182	[2]
Short-term debt	550	[2]	401	[2]
Other liabilities	2,393	[2]	2,031	[2]
Total liabilities	11,124	[2]	10,773	[2]
Total shareholders' equity	14,307	[2]	13,198	[2]
Total liabilities and shareholders' equity	25,431	[2]	23,971	[2]
Consolidating Adjustments [Member]
Condensed Financial Statements Captions [Line Items]
Investments in subsidiaries	(25,197)	[3]	(23,871)	[3]
Due from subsidiaries and affiliates, net	(376)	[3]	(498)	[3]
Total assets	(25,573)	[3]	(24,369)	[3]
Due to subsidiaries and affiliates, net	(376)	[3]	(498)	[3]
Total liabilities	(376)	[3]	(498)	[3]
Total shareholders' equity	(25,197)	[3]	(23,871)	[3]
Total liabilities and shareholders' equity	$ (25,573)	[3]	$ (24,369)	[3]

[1] ACE maintains two notional multi-currency cash pools (Pools) with a third-party bank. Various ACE entities participate in one or the other of the Pools, pursuant to which credit and debit balances in individual ACE accounts are translated daily into a single currency and pooled on a notional basis. Individual ACE entities are permitted to overdraw on their individual accounts provided the overall Pool balances do not fall below zero. At March 31, 2011 and December 31, 2010, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

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

[3] Includes ACE Limited parent company eliminations.