Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012		Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Investments	$ 59,690		$ 60,264
Cash	679	[1]	615	[2]	617		614
Insurance and reinsurance balances receivable	5,022		4,147
Reinsurance recoverable on losses and loss expenses	11,442		12,078
Reinsurance recoverable on policy benefits	240		241
Value of business acquired	560		614
Goodwill and other intangible assets	5,395		4,975
Other assets	10,660		9,611
Total assets	93,688		92,545
Unpaid losses and loss expenses	37,343		37,946
Unearned premiums	7,851		6,864
Future policy benefits	4,502		4,470
Short-term debt	1,901		1,401
Long-term debt	3,807		3,360
Trust preferred securities	309		309
Other liabilities	10,680		10,664
Total liabilities	66,393		65,014
Total shareholders' equity	27,295		27,531		25,762
Total liabilities and shareholders' equity	93,688		92,545
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	29		31
Cash	(513)	[1]	103	[2]	(30)		106
Investments in subsidiaries	27,409		27,251
Due from subsidiaries and affiliates, net	591		204
Other assets	6		13
Total assets	27,522		27,602
Other liabilities	227		71
Total liabilities	227		71
Total shareholders' equity	27,295		27,531
Total liabilities and shareholders' equity	27,522		27,602
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	31,387		31,074
Cash	583	[1]	515	[2]	508		382
Insurance and reinsurance balances receivable	4,371		3,654
Reinsurance recoverable on losses and loss expenses	16,277		17,232
Reinsurance recoverable on policy benefits	1,181		1,187
Value of business acquired	557		610
Goodwill and other intangible assets	4,843		4,419
Other assets	8,507		7,563
Total assets	67,706		66,254
Unpaid losses and loss expenses	30,894		31,356
Unearned premiums	6,644		5,872
Future policy benefits	3,915		3,876
Due to subsidiaries and affiliates, net	859		384
Short-term debt	1,351		851
Long-term debt	3,807		3,360
Trust preferred securities	309		309
Other liabilities	8,557		8,272
Total liabilities	56,336		54,280
Total shareholders' equity	11,370		11,974
Total liabilities and shareholders' equity	67,706		66,254
Other Ace Limited Subsidiaries And Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	28,274	[3]	29,159	[3]
Cash	609	[1],[3],[4]	(3)	[2],[3],[4]	139	[4]	126	[4]
Insurance and reinsurance balances receivable	651	[3]	493	[3]
Reinsurance recoverable on losses and loss expenses	(4,835)	[3]	(5,154)	[3]
Reinsurance recoverable on policy benefits	(941)	[3]	(946)	[3]
Value of business acquired	3	[3]	4	[3]
Goodwill and other intangible assets	552	[3]	556	[3]
Other assets	2,147	[3]	2,035	[3]
Total assets	26,460	[3]	26,144	[3]
Unpaid losses and loss expenses	6,449	[3]	6,590	[3]
Unearned premiums	1,207	[3]	992	[3]
Future policy benefits	587	[3]	594	[3]
Due to subsidiaries and affiliates, net	(268)	[3]	(180)	[3]
Short-term debt	550	[3]	550	[3]
Other liabilities	1,896	[3]	2,321	[3]
Total liabilities	10,421	[3]	10,867	[3]
Total shareholders' equity	16,039	[3]	15,277	[3]
Total liabilities and shareholders' equity	26,460	[3]	26,144	[3]
Consolidation, Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Investments in subsidiaries	(27,409)	[5]	(27,251)	[5]
Due from subsidiaries and affiliates, net	(591)	[5]	(204)	[5]
Total assets	(28,000)	[5]	(27,455)	[5]
Due to subsidiaries and affiliates, net	(591)	[5]	(204)	[5]
Total liabilities	(591)	[5]	(204)	[5]
Total shareholders' equity	(27,409)	[5]	(27,251)	[5]
Total liabilities and shareholders' equity	$ (28,000)	[5]	$ (27,455)	[5]

[1] ACE maintains two notional multicurrency 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 June 30, 2013, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[2] ACE maintains two notional multicurrency 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 December 31, 2012, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[3] Includes all other subsidiaries of ACE Limited and intercompany eliminations, primarily intercompany reinsurance transactions.

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

[5] Includes ACE Limited parent company eliminations.