Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Balance Sheet) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Condensed Financial Statements, Captions [Line Items]
Investments	$ 60,264		$ 55,676
Cash	615	[1],[2]	614		772	[3],[4]	669	[3]
Insurance and reinsurance balances receivable	4,147		4,387
Reinsurance recoverable on losses and loss expenses	12,078		12,389
Reinsurance recoverable on policy benefits	241		249
Value of business acquired	614		676
Goodwill and other intangible assets	4,975		4,799
Investments in subsidiaries
Due from subsidiaries and affiliates, net
Other assets	9,611		8,531
Total assets	92,545		87,321
Unpaid losses and loss expenses	37,946		37,477		37,391		37,783
Unearned premiums	6,864		6,334
Future policy benefits	4,470		4,274
Due to subsidiaries and affiliates, net
Short-term debt	1,401		1,251
Long-term debt	3,360		3,360
Trust preferred securities	309		309
Other liabilities	10,664		9,984
Total liabilities	65,014		62,989
Total shareholders' equity	27,531		24,332		22,835
Total liabilities and shareholders' equity	92,545		87,321
ACE limited (Parent Gurantor)
Condensed Financial Statements, Captions [Line Items]
Investments	31		33
Cash	103	[1],[2]	106		308	[4]	(1)	[3]
Insurance and reinsurance balances receivable
Reinsurance recoverable on losses and loss expenses
Reinsurance recoverable on policy benefits
Value of business acquired
Goodwill and other intangible assets
Investments in subsidiaries	27,251		23,871
Due from subsidiaries and affiliates, net	204		498
Other assets	13		8
Total assets	27,602		24,516
Unpaid losses and loss expenses
Unearned premiums
Future policy benefits
Due to subsidiaries and affiliates, net
Short-term debt
Long-term debt
Trust preferred securities
Other liabilities	71		184
Total liabilities	71		184
Total shareholders' equity	27,531		24,332
Total liabilities and shareholders' equity	27,602		24,516
ACE INA Holdings Inc. (Subsidiary Issuer)
Condensed Financial Statements, Captions [Line Items]
Investments	31,074		28,848
Cash	515	[1],[2]	382		573	[4]	400	[3]
Insurance and reinsurance balances receivable	3,654		3,944
Reinsurance recoverable on losses and loss expenses	17,232		17,146
Reinsurance recoverable on policy benefits	1,187		941
Value of business acquired	610		676
Goodwill and other intangible assets	4,419		4,248
Investments in subsidiaries
Due from subsidiaries and affiliates, net
Other assets	7,563		7,018
Total assets	66,254		63,203
Unpaid losses and loss expenses	31,356		30,837
Unearned premiums	5,872		5,416
Future policy benefits	3,876		3,673
Due to subsidiaries and affiliates, net	384		316
Short-term debt	851		850
Long-term debt	3,360		3,360
Trust preferred securities	309		309
Other liabilities	8,272		7,769
Total liabilities	54,280		52,530
Total shareholders' equity	11,974		10,673
Total liabilities and shareholders' equity	66,254		63,203
Other ACE Limited Subsidiaries and Eliminations
Condensed Financial Statements, Captions [Line Items]
Investments	29,159	[5]	26,795	[5]
Cash	(3)	[1],[2],[5]	126	[5]	(109)	[4],[5]	270	[3],[5]
Insurance and reinsurance balances receivable	493	[5]	443	[5]
Reinsurance recoverable on losses and loss expenses	(5,154)	[5]	(4,757)	[5]
Reinsurance recoverable on policy benefits	(946)	[5]	(692)	[5]
Value of business acquired	4	[5]		[5]
Goodwill and other intangible assets	556	[5]	551	[5]
Investments in subsidiaries		[5]		[5]
Due from subsidiaries and affiliates, net		[5]		[5]
Other assets	2,035	[5]	1,505	[5]
Total assets	26,144	[5]	23,971	[5]
Unpaid losses and loss expenses	6,590	[5]	6,640	[5]
Unearned premiums	992	[5]	918	[5]
Future policy benefits	594	[5]	601	[5]
Due to subsidiaries and affiliates, net	(180)	[5]	182	[5]
Short-term debt	550	[5]	401	[5]
Long-term debt		[5]		[5]
Trust preferred securities		[5]		[5]
Other liabilities	2,321	[5]	2,031	[5]
Total liabilities	10,867	[5]	10,773	[5]
Total shareholders' equity	15,277	[5]	13,198	[5]
Total liabilities and shareholders' equity	26,144	[5]	23,971	[5]
Consolidating Adjustments
Condensed Financial Statements, Captions [Line Items]
Investments		[6]		[6]
Cash		[1],[2],[6],[7]		[6],[7]	0	[4],[7]		[3]
Insurance and reinsurance balances receivable		[6]		[6]
Reinsurance recoverable on losses and loss expenses		[6]		[6]
Reinsurance recoverable on policy benefits		[6]		[6]
Value of business acquired		[6]		[6]
Goodwill and other intangible assets		[6]		[6]
Investments in subsidiaries	(27,251)	[6]	(23,871)	[6]
Due from subsidiaries and affiliates, net	(204)	[6]	(498)	[6]
Other assets		[6]		[6]
Total assets	(27,455)	[6]	(24,369)	[6]
Unpaid losses and loss expenses		[6]		[6]
Unearned premiums		[6]		[6]
Future policy benefits		[6]		[6]
Due to subsidiaries and affiliates, net	(204)	[6]	(498)	[6]
Short-term debt		[6]		[6]
Long-term debt		[6]		[6]
Trust preferred securities		[6]		[6]
Other liabilities		[6]		[6]
Total liabilities	(204)	[6]	(498)	[6]
Total shareholders' equity	(27,251)	[6]	(23,871)	[6]
Total liabilities and shareholders' equity	$ (27,455)	[6]	$ (24,369)	[6]

[1] ACE maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1f) for additional information. At December 31, 2012, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[2] ACE maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2012, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[3] ACE maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2010 and 2009, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[4] ACE maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2010, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

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

[6] Includes ACE Limited parent company eliminations.

[7] Includes ACE Limited parent company eliminations