Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions	Sep. 30, 2015		Dec. 31, 2014		Sep. 30, 2014		Dec. 31, 2013	[4]
Condensed Financial Statements, Captions [Line Items]
Investments	$ 62,384		$ 62,904
Cash	1,038	[1],[2]	655	[1],[3]	$ 806	[4]	$ 579
Insurance and reinsurance balances receivable	5,290		5,426
Reinsurance recoverable on losses and loss expenses	11,231		11,992
Reinsurance recoverable on policy benefits	194		217
Value of business acquired	410		466
Goodwill and other intangible assets	5,713		5,724
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	11,500		10,864
Total assets	97,760		98,248
Unpaid losses and loss expenses	37,564		38,315
Unearned premiums	8,510		8,222
Future policy benefits	4,776		4,754
Due to subsidiaries and affiliates, net	0		0
Short-term debt	2,103		2,552
Affiliated notional cash pooling programs	0		0
Long-term debt	4,157		3,357
Trust preferred securities	309		309
Other liabilities	11,214		11,152
Total liabilities	68,633		68,661
Total shareholders' equity	29,127		29,587		30,017
Total liabilities and shareholders’ equity	97,760		98,248
ACE Limited (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Investments	29		30
Cash	17	[1],[2]	0	[1],[3]	8	[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	29,441		29,497
Due from subsidiaries and affiliates, net	866		583
Other assets	9		4
Total assets	30,362		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	973	[2]	246	[3]
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	262		281
Total liabilities	1,235		527
Total shareholders' equity	29,127		29,587
Total liabilities and shareholders’ equity	30,362		30,114
ACE INA Holdings Inc (Subsidiary Issuer)
Condensed Financial Statements, Captions [Line Items]
Investments	35		225
Cash	5	[1],[2]	1	[1],[3]	12	[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	19,184		18,762
Due from subsidiaries and affiliates, net	0		0
Other assets	272		295
Total assets	19,496		19,283
Unpaid losses and loss expenses	0		0
Unearned premiums			0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	698		422
Short-term debt	700		1,150
Affiliated notional cash pooling programs	188	[2]	309	[3]
Long-term debt	4,145		3,345
Trust preferred securities	309		309
Other liabilities	1,458		1,404
Total liabilities	7,498		6,939
Total shareholders' equity	11,998		12,344
Total liabilities and shareholders’ equity	19,496		19,283
Other ACE Limited Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Investments	62,320		62,649
Cash	2,177	[1],[2]	1,209	[1],[3]	1,391	[4]	748
Insurance and reinsurance balances receivable	6,284		6,178
Reinsurance recoverable on losses and loss expenses	20,039		20,992
Reinsurance recoverable on policy benefits	1,148		1,194
Value of business acquired	410		466
Goodwill and other intangible assets	5,713		5,724
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	14,880		14,196
Total assets	112,971		112,608
Unpaid losses and loss expenses	45,810		46,770
Unearned premiums	10,329		9,958
Future policy benefits	5,730		5,731
Due to subsidiaries and affiliates, net	168		161
Short-term debt	1,403		1,402
Affiliated notional cash pooling programs	0	[2]	0	[3]
Long-term debt	12		12
Trust preferred securities	0		0
Other liabilities	12,892		12,659
Total liabilities	76,344		76,693
Total shareholders' equity	36,627		35,915
Total liabilities and shareholders’ equity	112,971		112,608
Consolidating Adjustments and Eliminations
Condensed Financial Statements, Captions [Line Items]
Investments	0		0
Cash	(1,161)	[1],[2]	(555)	[1],[3]	$ (605)	[4]	$ (185)
Insurance and reinsurance balances receivable	(994)		(752)
Reinsurance recoverable on losses and loss expenses	(8,808)		(9,000)
Reinsurance recoverable on policy benefits	(954)		(977)
Value of business acquired	0		0
Goodwill and other intangible assets	0		0
Investments in subsidiaries	(48,625)		(48,259)
Due from subsidiaries and affiliates, net	(866)		(583)
Other assets	(3,661)		(3,631)
Total assets	(65,069)		(63,757)
Unpaid losses and loss expenses	(8,246)		(8,455)
Unearned premiums	(1,819)		(1,736)
Future policy benefits	(954)		(977)
Due to subsidiaries and affiliates, net	(866)		(583)
Short-term debt	0		0
Affiliated notional cash pooling programs	(1,161)	[2]	(555)	[3]
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	(3,398)		(3,192)
Total liabilities	(16,444)		(15,498)
Total shareholders' equity	(48,625)		(48,259)
Total liabilities and shareholders’ equity	$ (65,069)		$ (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 September 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 September 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 September 30, 2014 and December 31, 2013, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.