Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	$ 1,075		$ 1,250
Purchases of fixed maturities available for sale	(4,336)		(3,522)
Purchases of fixed maturities held to maturity	(21)		(30)
Purchases of equity securities	(39)		(37)
Sales of fixed maturities available for sale	2,002		2,208
Sales of equity securities	28		27
Maturities and redemptions of fixed maturities available for sale	1,481		1,550
Maturities and redemptions of fixed maturities held to maturity	324		212
Net change in short-term investments	(255)		(765)
Net derivative instruments settlements	(51)		(96)
Cash Acquired from Acquisition	0
Other	(153)		(50)
Net cash flows used for investing activities	(1,020)		(503)
Dividends paid on Common Shares	(214)		(214)
Common Shares repurchased	(347)		(335)
Proceeds from issuance of long-term debt	800		0
Proceeds from issuance of short-term debt	477		426
Repayments of Short-term Debt	(477)		(426)
Proceeds from share-based compensation plans, including windfall tax benefits	39		40
Advances To From Affiliates Financing Activities	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	0		0
Policyholder contract deposits	101		51
Policyholder contract withdrawals	(40)		(14)
Other	(6)		0
Net cash flows (used for) from financing activities	333		(472)
Effect of foreign currency rate changes on cash and cash equivalents	(95)		(7)
Net increase in cash	293		268
Cash – beginning of period	655	[1],[2]	579	[3]
Cash – end of period	948	[1],[4]	847	[3]
ACE Limited (Parent Guarantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	48		57
Purchases of fixed maturities available for sale	0		0
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Sales of fixed maturities available for sale	0		0
Sales of equity securities	0		0
Maturities and redemptions of fixed maturities available for sale	0		0
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	0		0
Net derivative instruments settlements	0		0
Other	0		0
Net cash flows used for investing activities	0		0
Dividends paid on Common Shares	(214)		(214)
Common Shares repurchased	0		0
Proceeds from issuance of long-term debt	0
Proceeds from issuance of short-term debt	0		0
Repayments of Short-term Debt	0
Proceeds from share-based compensation plans, including windfall tax benefits	0		0
Advances To From Affiliates Financing Activities	336		367
Net proceeds from (payments to) affiliated notional cash pooling program	(168)	[1]	(185)	[3]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Other	0
Net cash flows (used for) from financing activities	(46)		(32)
Effect of foreign currency rate changes on cash and cash equivalents	0		0
Net increase in cash	2		25
Cash – beginning of period	0	[1],[2]	0	[3]
Cash – end of period	2	[1],[4]	25	[3]
ACE INA Holdings Inc (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	4		(13)
Purchases of fixed maturities available for sale	0		0
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Sales of fixed maturities available for sale	0		0
Sales of equity securities	0		0
Maturities and redemptions of fixed maturities available for sale	0		0
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	216		(8)
Net derivative instruments settlements	0		(9)
Other	0		(3)
Net cash flows used for investing activities	216		(20)
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		0
Proceeds from issuance of long-term debt	800
Proceeds from issuance of short-term debt	0		0
Repayments of Short-term Debt	0
Proceeds from share-based compensation plans, including windfall tax benefits	0		0
Advances To From Affiliates Financing Activities	(340)		(367)
Net proceeds from (payments to) affiliated notional cash pooling program	(309)	[1]	385	[3]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Other	(6)
Net cash flows (used for) from financing activities	145		18
Effect of foreign currency rate changes on cash and cash equivalents	0		0
Net increase in cash	365		(15)
Cash – beginning of period	1	[1],[2]	16	[3]
Cash – end of period	366	[1],[4]	1	[3]
Other ACE Limited Subsidiaries
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	1,023		1,206
Purchases of fixed maturities available for sale	(4,336)		(3,522)
Purchases of fixed maturities held to maturity	(21)		(30)
Purchases of equity securities	(39)		(37)
Sales of fixed maturities available for sale	2,002		2,208
Sales of equity securities	28		27
Maturities and redemptions of fixed maturities available for sale	1,481		1,550
Maturities and redemptions of fixed maturities held to maturity	324		212
Net change in short-term investments	(471)		(757)
Net derivative instruments settlements	(51)		(87)
Other	(153)		(47)
Net cash flows used for investing activities	(1,236)		(483)
Dividends paid on Common Shares	0		0
Common Shares repurchased	(347)		(335)
Proceeds from issuance of long-term debt	0
Proceeds from issuance of short-term debt	477		426
Repayments of Short-term Debt	(477)
Proceeds from share-based compensation plans, including windfall tax benefits	39		40
Advances To From Affiliates Financing Activities	4		0
Net proceeds from (payments to) affiliated notional cash pooling program	0	[1]	0	[3]
Policyholder contract deposits	101		51
Policyholder contract withdrawals	(40)		(14)
Other	0
Net cash flows (used for) from financing activities	(243)		(258)
Effect of foreign currency rate changes on cash and cash equivalents	(95)		(7)
Net increase in cash	(551)		458
Cash – beginning of period	1,209	[1],[2]	748	[3]
Cash – end of period	658	[1],[4]	1,206	[3]
Consolidating Adjustments and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	0		0
Purchases of fixed maturities available for sale	0		0
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Sales of fixed maturities available for sale	0		0
Sales of equity securities	0		0
Maturities and redemptions of fixed maturities available for sale	0		0
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	0		0
Net derivative instruments settlements	0		0
Other	0		0
Net cash flows used for investing activities	0		0
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		0
Proceeds from issuance of long-term debt	0
Proceeds from issuance of short-term debt	0		0
Repayments of Short-term Debt	0
Proceeds from share-based compensation plans, including windfall tax benefits	0		0
Advances To From Affiliates Financing Activities	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	477	[1]	(200)	[3]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Other	0
Net cash flows (used for) from financing activities	477		(200)
Effect of foreign currency rate changes on cash and cash equivalents	0		0
Net increase in cash	477		(200)
Cash – beginning of period	(555)	[1],[2]	(185)	[3]
Cash – end of period	$ (78)	[1],[4]	$ (385)	[3]

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