Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014		Mar. 31, 2014		Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Investments	$ 63,894		$ 62,904
Cash	948	[1],[2]	655	[1],[3]	847	[4]	579	[4]
Insurance and reinsurance balances receivable	5,026		5,426
Reinsurance recoverable on losses and loss expenses	11,588		11,992
Reinsurance recoverable on policy benefits	215		217
Value of business acquired	440		466
Goodwill and other intangible assets	5,516		5,724
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	10,771		10,864
Total assets	98,398		98,248
Unpaid losses and loss expenses	37,326		38,315
Unearned premiums	8,182		8,222
Future policy benefits	4,744		4,754
Due to subsidiaries and affiliates, net	0		0
Short-term debt	2,552		2,552
Affiliated notional cash pooling programs	0		0
Long-term debt	4,157		3,357
Trust preferred securities	309		309
Other liabilities	11,426		11,152
Total liabilities	68,696		68,661
Total shareholders' equity	29,702		29,587		29,369
Total liabilities and shareholders’ equity	98,398		98,248
ACE Limited (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Investments	31		30
Cash	2	[1],[2]	0	[1],[3]	25	[4]	0	[4]
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	29,798		29,497
Due from subsidiaries and affiliates, net	233		583
Other assets	4		4
Total assets	30,068		30,114
Unpaid losses and loss expenses	0		0
Unearned premiums	0		0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	0		0
Short-term debt	0		0
Affiliated notional cash pooling programs	78	[2]	246	[3]
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	288		281
Total liabilities	366		527
Total shareholders' equity	29,702		29,587
Total liabilities and shareholders’ equity	30,068		30,114
ACE INA Holdings Inc (Subsidiary Issuer)
Condensed Financial Statements, Captions [Line Items]
Investments	10		225
Cash	366	[1],[2]	1	[1],[3]	1	[4]	16	[4]
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	18,767		18,762
Due from subsidiaries and affiliates, net	0		0
Other assets	291		295
Total assets	19,434		19,283
Unpaid losses and loss expenses	0		0
Unearned premiums	0		0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	103		422
Short-term debt	1,150		1,150
Affiliated notional cash pooling programs	0	[2]	309	[3]
Long-term debt	4,145		3,345
Trust preferred securities	309		309
Other liabilities	1,434		1,404
Total liabilities	7,141		6,939
Total shareholders' equity	12,293		12,344
Total liabilities and shareholders’ equity	19,434		19,283
Other ACE Limited Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Investments	63,853		62,649
Cash	658	[1],[2]	1,209	[1],[3]	1,206	[4]	748	[4]
Insurance and reinsurance balances receivable	5,746		6,178
Reinsurance recoverable on losses and loss expenses	20,292		20,992
Reinsurance recoverable on policy benefits	1,171		1,194
Value of business acquired	440		466
Goodwill and other intangible assets	5,516		5,724
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	14,088		14,196
Total assets	111,764		112,608
Unpaid losses and loss expenses	45,518		46,770
Unearned premiums	9,912		9,958
Future policy benefits	5,700		5,731
Due to subsidiaries and affiliates, net	130		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	12,818		12,659
Total liabilities	75,492		76,693
Total shareholders' equity	36,272		35,915
Total liabilities and shareholders’ equity	111,764		112,608
Consolidating Adjustments and Eliminations
Condensed Financial Statements, Captions [Line Items]
Investments	0		0
Cash	(78)	[1],[2]	(555)	[1],[3]	(385)	[4]	(185)	[4]
Insurance and reinsurance balances receivable	(720)		(752)
Reinsurance recoverable on losses and loss expenses	(8,704)		(9,000)
Reinsurance recoverable on policy benefits	(956)		(977)
Value of business acquired	0		0
Goodwill and other intangible assets	0		0
Investments in subsidiaries	(48,565)		(48,259)
Due from subsidiaries and affiliates, net	(233)		(583)
Other assets	(3,612)		(3,631)
Total assets	(62,868)		(63,757)
Unpaid losses and loss expenses	(8,192)		(8,455)
Unearned premiums	(1,730)		(1,736)
Future policy benefits	(956)		(977)
Due to subsidiaries and affiliates, net	(233)		(583)
Short-term debt	0		0
Affiliated notional cash pooling programs	(78)	[2]	(555)	[3]
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	(3,114)		(3,192)
Total liabilities	(14,303)		(15,498)
Total shareholders' equity	(48,565)		(48,259)
Total liabilities and shareholders’ equity	$ (62,868)		$ (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 March 31, 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 March 31, 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 March 31, 2014 and December 31, 2013, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.