Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions	Jun. 30, 2015		Dec. 31, 2014		Jun. 30, 2014		Dec. 31, 2013	[4]
Condensed Financial Statements, Captions [Line Items]
Investments	$ 63,265		$ 62,904
Cash	790	[1],[2]	655	[1],[3]	$ 594	[4]	$ 579
Insurance and reinsurance balances receivable	5,757		5,426
Reinsurance recoverable on losses and loss expenses	11,775		11,992
Reinsurance recoverable on policy benefits	203		217
Value of business acquired	434		466
Goodwill and other intangible assets	5,969		5,724
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	11,647		10,864
Total assets	99,840		98,248
Unpaid losses and loss expenses	38,230		38,315
Unearned premiums	8,879		8,222
Future policy benefits	4,835		4,754
Due to subsidiaries and affiliates, net	0		0
Short-term debt	2,102		2,552
Affiliated notional cash pooling programs	0		0
Long-term debt	4,157		3,357
Trust preferred securities	309		309
Other liabilities	11,773		11,152
Total liabilities	70,285		68,661
Total shareholders' equity	29,555		29,587		30,325
Total liabilities and shareholders’ equity	99,840		98,248
ACE Limited (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Investments	32		30
Cash	1	[1],[2]	0	[1],[3]	44	[4]	0
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	29,806		29,497
Due from subsidiaries and affiliates, net	370		583
Other assets	5		4
Total assets	30,214		30,114
Unpaid losses and loss expenses	0		0
Unearned premiums			0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	0		0
Short-term debt	0		0
Affiliated notional cash pooling programs	386	[2]	246	[3]
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	273		281
Total liabilities	659		527
Total shareholders' equity	29,555		29,587
Total liabilities and shareholders’ equity	30,214		30,114
ACE INA Holdings Inc (Subsidiary Issuer)
Condensed Financial Statements, Captions [Line Items]
Investments	35		225
Cash	3	[1],[2]	1	[1],[3]	1	[4]	16
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	18,747		18,762
Due from subsidiaries and affiliates, net	0		0
Other assets	381		295
Total assets	19,166		19,283
Unpaid losses and loss expenses	0		0
Unearned premiums			0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	245		422
Short-term debt	700		1,150
Affiliated notional cash pooling programs	37	[2]	309	[3]
Long-term debt	4,145		3,345
Trust preferred securities	309		309
Other liabilities	1,499		1,404
Total liabilities	6,935		6,939
Total shareholders' equity	12,231		12,344
Total liabilities and shareholders’ equity	19,166		19,283
Other ACE Limited Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Investments	63,198		62,649
Cash	1,209	[1],[2]	1,209	[1],[3]	1,026	[4]	748
Insurance and reinsurance balances receivable	6,726		6,178
Reinsurance recoverable on losses and loss expenses	20,619		20,992
Reinsurance recoverable on policy benefits	1,192		1,194
Value of business acquired	434		466
Goodwill and other intangible assets	5,969		5,724
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	15,026		14,196
Total assets	114,373		112,608
Unpaid losses and loss expenses	46,596		46,770
Unearned premiums	10,718		9,958
Future policy benefits	5,824		5,731
Due to subsidiaries and affiliates, net	125		161
Short-term debt	1,402		1,402
Affiliated notional cash pooling programs	0	[2]	0	[3]
Long-term debt	12		12
Trust preferred securities	0		0
Other liabilities	13,374		12,659
Total liabilities	78,051		76,693
Total shareholders' equity	36,322		35,915
Total liabilities and shareholders’ equity	114,373		112,608
Consolidating Adjustments and Eliminations
Condensed Financial Statements, Captions [Line Items]
Investments	0		0
Cash	(423)	[1],[2]	(555)	[1],[3]	$ (477)	[4]	$ (185)
Insurance and reinsurance balances receivable	(969)		(752)
Reinsurance recoverable on losses and loss expenses	(8,844)		(9,000)
Reinsurance recoverable on policy benefits	(989)		(977)
Value of business acquired	0		0
Goodwill and other intangible assets	0		0
Investments in subsidiaries	(48,553)		(48,259)
Due from subsidiaries and affiliates, net	(370)		(583)
Other assets	(3,765)		(3,631)
Total assets	(63,913)		(63,757)
Unpaid losses and loss expenses	(8,366)		(8,455)
Unearned premiums	(1,839)		(1,736)
Future policy benefits	(989)		(977)
Due to subsidiaries and affiliates, net	(370)		(583)
Short-term debt	0		0
Affiliated notional cash pooling programs	(423)	[2]	(555)	[3]
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	(3,373)		(3,192)
Total liabilities	(15,360)		(15,498)
Total shareholders' equity	(48,553)		(48,259)
Total liabilities and shareholders’ equity	$ (63,913)		$ (63,757)

[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, 2015 and December 31, 2014, 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 June 30, 2015, 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, 2014, 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 June 30, 2014 and December 31, 2013, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.