Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012		Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Investments	$ 60,342		$ 60,264
Insurance and reinsurance balances receivable	5,089		4,147
Reinsurance recoverable on losses and loss expenses	11,477		12,078
Reinsurance recoverable on policy benefits	237		241
Value of business acquired	554		614
Goodwill and other intangible assets	5,465		4,975
Other assets	10,652		9,611
Total assets	94,584		92,545
Unpaid losses and loss expenses	37,882		37,946
Unearned premiums	7,794		6,864
Future policy benefits	4,596		4,470
Short-term debt	1,902		1,401
Long-term debt	3,807		3,360
Trust preferred securities	309		309
Other liabilities	10,076		10,664
Total liabilities	66,366		65,014
Total shareholders' equity	28,218		27,531		26,963
Total liabilities and shareholders’ equity	94,584		92,545
Cash	768	[1],[2]	615	[2],[3]	690	[4]	614	[4]
Scenario, Previously Reported [Member]
Condensed Financial Statements, Captions [Line Items]
Investments			60,264
Insurance and reinsurance balances receivable			4,147
Reinsurance recoverable on losses and loss expenses			12,078
Reinsurance recoverable on policy benefits			241
Value of business acquired			614
Goodwill and other intangible assets			4,975
Other assets			9,611
Total assets			92,545
Unpaid losses and loss expenses			37,946
Unearned premiums			6,864
Future policy benefits			4,470
Short-term debt			1,401
Long-term debt			3,360
Trust preferred securities			309
Other liabilities			10,664
Total liabilities			65,014
Total shareholders' equity			27,531
Total liabilities and shareholders’ equity			92,545
Cash			615	[3]	690	[4]	614
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	29		31
Investments in subsidiaries	28,457		27,251
Due from subsidiaries and affiliates, net	813		204
Other assets	5		13
Total assets	29,315		27,602
Affiliated notional cash pooling programs	872	[1]
Trust preferred securities			0
Other liabilities	225		71
Total liabilities	1,097		71
Total shareholders' equity	28,218		27,531
Total liabilities and shareholders’ equity	29,315		27,602
Cash	11	[1],[2]	103	[2],[3]	0	[4]	106	[4]
Parent Company [Member] | Scenario, Previously Reported [Member]
Condensed Financial Statements, Captions [Line Items]
Investments			31
Investments in subsidiaries			27,251
Due from subsidiaries and affiliates, net			204
Other assets			13
Total assets			27,602
Trust preferred securities			0
Other liabilities			71
Total liabilities			71
Total shareholders' equity			27,531
Total liabilities and shareholders’ equity			27,602
Cash			103	[3]	(116)	[4]	106
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	10		14
Insurance and reinsurance balances receivable	0		0
Reinsurance recoverable on losses and loss expenses	0		0
Reinsurance recoverable on policy benefits	0		0
Value of business acquired	0		0
Goodwill and other intangible assets	0		0
Investments in subsidiaries	17,979		17,016
Other assets	219		210
Total assets	18,373		17,242
Unpaid losses and loss expenses	0		0
Unearned premiums	0		0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	661		68
Short-term debt	500		0
Affiliated notional cash pooling programs	0	[1]	349	[1]
Long-term debt	3,795		3,347
Trust preferred securities	309		309
Other liabilities	1,342		1,195
Total liabilities	6,607		5,268
Total shareholders' equity	11,766		11,974
Total liabilities and shareholders’ equity	18,373		17,242
Cash	165	[1],[2]	2	[2],[3]	32	[4]	5	[4]
Guarantor Subsidiaries [Member] | Scenario, Previously Reported [Member]
Condensed Financial Statements, Captions [Line Items]
Investments			31,074
Insurance and reinsurance balances receivable			3,654
Reinsurance recoverable on losses and loss expenses			17,232
Reinsurance recoverable on policy benefits			1,187
Value of business acquired			610
Goodwill and other intangible assets			4,419
Investments in subsidiaries			0
Other assets			7,563
Total assets			66,254
Unpaid losses and loss expenses			31,356
Unearned premiums			5,872
Future policy benefits			3,876
Due to subsidiaries and affiliates, net			384
Short-term debt			851
Long-term debt			3,360
Trust preferred securities			309
Other liabilities			8,272
Total liabilities			54,280
Total shareholders' equity			11,974
Total liabilities and shareholders’ equity			66,254
Cash			515	[3]	550	[4]	382
Other Ace Limited Subsidiaries And Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	60,303		60,219
Insurance and reinsurance balances receivable	6,225		4,742
Reinsurance recoverable on losses and loss expenses	20,279		20,935
Reinsurance recoverable on policy benefits	1,246		1,229
Value of business acquired	554		614
Goodwill and other intangible assets	5,465		4,975
Other assets	12,679		11,304
Total assets	108,215		104,877
Unpaid losses and loss expenses	46,215		46,109
Unearned premiums	9,523		8,248
Future policy benefits	5,605		5,458
Due to subsidiaries and affiliates, net	152		136
Short-term debt	1,402		1,401
Affiliated notional cash pooling programs	0	[1]	0	[1]
Long-term debt	12		13
Trust preferred securities			0
Other liabilities	10,636		11,219
Total liabilities	73,545		72,584
Total shareholders' equity	34,670		32,293
Total liabilities and shareholders’ equity	108,215		104,877
Cash	1,464	[1],[2]	859	[2],[3]	929	[4]	651	[4]
Other Ace Limited Subsidiaries And Eliminations [Member] | Scenario, Previously Reported [Member]
Condensed Financial Statements, Captions [Line Items]
Investments			29,159	[5]
Insurance and reinsurance balances receivable			493	[5]
Reinsurance recoverable on losses and loss expenses			(5,154)	[5]
Reinsurance recoverable on policy benefits			(946)	[5]
Value of business acquired			4	[5]
Goodwill and other intangible assets			556	[5]
Other assets			2,035	[5]
Total assets			26,144	[5]
Unpaid losses and loss expenses			6,590	[5]
Unearned premiums			992	[5]
Future policy benefits			594	[5]
Due to subsidiaries and affiliates, net			(180)	[5]
Short-term debt			550	[5]
Long-term debt			0	[5]
Trust preferred securities			0	[5]
Other liabilities			2,321	[5]
Total liabilities			10,867	[5]
Total shareholders' equity			15,277	[5]
Total liabilities and shareholders’ equity			26,144	[5]
Cash			(3)	[3],[5]	256	[4],[6]	126	[6]
Consolidation, Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Investments	0		0
Insurance and reinsurance balances receivable	(1,136)		(595)
Reinsurance recoverable on losses and loss expenses	(8,802)		(8,857)
Reinsurance recoverable on policy benefits	(1,009)		(988)
Value of business acquired	0		0
Goodwill and other intangible assets	0		0
Investments in subsidiaries	(46,436)		(44,267)
Due from subsidiaries and affiliates, net	(813)		(204)
Other assets	(2,251)		(1,916)
Total assets	(61,319)		(57,176)
Unpaid losses and loss expenses	(8,333)		(8,163)
Unearned premiums	(1,729)		(1,384)
Future policy benefits	(1,009)		(988)
Due to subsidiaries and affiliates, net	(813)		(204)
Short-term debt	0		0
Affiliated notional cash pooling programs	(872)	[1]	(349)	[1]
Long-term debt			0
Trust preferred securities			0
Other liabilities	(2,127)		(1,821)
Total liabilities	(14,883)		(12,909)
Total shareholders' equity	(46,436)		(44,267)
Total liabilities and shareholders’ equity	(61,319)		(57,176)
Cash	(872)	[1],[2]	(349)	[2],[3]	(271)	[4]	(148)	[4]
Consolidation, Eliminations [Member] | Scenario, Previously Reported [Member]
Condensed Financial Statements, Captions [Line Items]
Investments			0	[7]
Insurance and reinsurance balances receivable			0	[7]
Reinsurance recoverable on losses and loss expenses			0	[7]
Reinsurance recoverable on policy benefits			0	[7]
Value of business acquired			0	[7]
Goodwill and other intangible assets			0	[7]
Investments in subsidiaries			(27,251)	[7]
Due from subsidiaries and affiliates, net			(204)	[7]
Other assets			0	[7]
Total assets			(27,455)	[7]
Unpaid losses and loss expenses			0	[7]
Unearned premiums			0	[7]
Future policy benefits			0	[7]
Due to subsidiaries and affiliates, net			(204)	[7]
Short-term debt			0	[7]
Long-term debt			0	[7]
Trust preferred securities			0	[7]
Other liabilities			0	[7]
Total liabilities			(204)	[7]
Total shareholders' equity			(27,251)	[7]
Total liabilities and shareholders’ equity			(27,455)	[7]
Cash			$ 0	[3],[7]	$ 0	[4],[8]	$ 0	[8]

[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 September 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 September 30, 2013 and 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 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.

[4] 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 September 30, 2012 and December 31, 2011, 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, primarily intercompany reinsurance transactions.

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

[7] Includes ACE Limited parent company eliminations.

[8] Includes ACE Limited parent company eliminations and certain consolidating adjustments.