Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	$ 4,496		$ 4,022		$ 3,995
Purchases of fixed maturities available for sale	(15,553)		(21,398)		(23,961)
Purchases of fixed maturities held to maturity	(267)		(447)		(388)
Purchases of equity securities	(251)		(264)		(135)
Sales of fixed maturities available for sale	7,482		10,413		14,769
Sales of equity securities	670		142		119
Maturities and redemptions of fixed maturities available for sale	6,413		6,941		5,523
Maturities and redemptions of fixed maturities held to maturity	875		1,488		1,451
Net change in short-term investments	(603)		524		117
Net derivative instruments settlements	(230)		(471)		(281)
Acquisition of subsidiaries (net of cash acquired)	(766)		(977)		(98)
Capital contribution to subsidiary			0		0
Other	(274)		(393)		(555)
Net cash flows used for investing activities	(2,504)		(4,442)		(3,439)
Dividends paid on Common Shares	(862)		(517)		(815)
Common Shares repurchased	(1,429)		(287)		(11)
Proceeds from issuance of long-term debt	699		947
Proceeds from issuance of short-term debt	1,978		2,572		2,933
Repayments of Long-term Debt	(501)
Repayments of Short-term Debt	(1,977)		(2,572)		(2,783)
Proceeds from share-based compensation plans	127		135		126
Advances from (to) affiliates					0
Capital contribution from subsidiary			0		0
Net proceeds from (payments to) affiliated notional cash pooling programs					0	[1]
Dividends to parent company					0
Other	188		113
Net cash flows (used for) from financing activities	(1,777)		391		(550)
Effect of foreign currency rate changes on cash and cash equivalents	(139)		(7)		(5)
Net increase (decrease) in cash	76		(36)		1
Cash – beginning of year	579	[2],[3],[4]	615	[1],[2]	614	[1]
Cash – end of year	655	[3],[5]	579	[2],[3],[4]	615	[1],[2]
ACE limited (Parent Gurantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	541		970		573
Purchases of fixed maturities available for sale					0
Purchases of fixed maturities held to maturity					0
Purchases of equity securities					0
Sales of fixed maturities available for sale					0
Sales of equity securities					0
Maturities and redemptions of fixed maturities available for sale					0
Maturities and redemptions of fixed maturities held to maturity					0
Net change in short-term investments	0		(1)		0
Net derivative instruments settlements	0		0		(1)
Advances from (to) affiliates	260		(621)		206
Acquisition of subsidiaries (net of cash acquired)					0
Capital contribution to subsidiary			(133)		0
Other					0
Net cash flows used for investing activities	0		(134)		(1)
Dividends paid on Common Shares	(862)		(517)		(815)
Common Shares repurchased					0
Proceeds from issuance of long-term debt	0
Proceeds from issuance of short-term debt					130
Repayments of Short-term Debt					(130)
Net proceeds from (repayments) issuance of short-term debt			0
Proceeds from share-based compensation plans	0		14		34
Advances from (to) affiliates	260		(621)		206
Capital contribution from subsidiary			0		0
Net proceeds from (payments to) affiliated notional cash pooling programs	61	[3]	185	[2]	0
Dividends to parent company			0		0
Net cash flows (used for) from financing activities	(541)		(939)		(575)
Effect of foreign currency rate changes on cash and cash equivalents					0
Net increase (decrease) in cash	0		(103)		(3)
Cash – beginning of year	0		103	[1],[2]	106	[1]
Cash – end of year	0	[3],[5]	0		103	[1],[2]
ACE INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	210		(107)		296
Purchases of fixed maturities available for sale					0
Purchases of fixed maturities held to maturity					0
Purchases of equity securities					0
Sales of fixed maturities available for sale					0
Sales of equity securities					0
Maturities and redemptions of fixed maturities available for sale					0
Maturities and redemptions of fixed maturities held to maturity					0
Net change in short-term investments	(216)		4		(4)
Net derivative instruments settlements	53		(1)		0
Acquisition of subsidiaries (net of cash acquired)					0
Capital contribution to subsidiary	(258)		(1,097)		(352)
Other	(8)		(4)		(33)
Net cash flows used for investing activities	(429)		(1,098)		(389)
Dividends paid on Common Shares					0
Common Shares repurchased					0
Proceeds from issuance of long-term debt	699		947
Proceeds from issuance of short-term debt					0
Repayments of Long-term Debt	(500)
Proceeds from share-based compensation plans	0				0
Advances from (to) affiliates	(298)		621		(201)
Capital contribution from subsidiary			0		90
Net proceeds from (payments to) affiliated notional cash pooling programs	309	[3]	(349)	[2]	201	[1]
Dividends to parent company			0		0
Other	(6)
Net cash flows (used for) from financing activities	204		1,219		90
Effect of foreign currency rate changes on cash and cash equivalents					0
Net increase (decrease) in cash	(15)		14		(3)
Cash – beginning of year	16	[2],[3],[4]	2	[1],[2]	5	[1]
Cash – end of year	1	[3],[5]	16	[2],[3],[4]	2	[1],[2]
Other ACE Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	4,419		3,984		3,876
Purchases of fixed maturities available for sale	(15,816)		(21,504)		(24,076)
Purchases of fixed maturities held to maturity	(267)		(447)		(388)
Purchases of equity securities	(251)		(264)		(135)
Sales of fixed maturities available for sale	7,750		10,519		14,884
Sales of equity securities	670		142		119
Maturities and redemptions of fixed maturities available for sale	6,413		6,941		5,523
Maturities and redemptions of fixed maturities held to maturity	875		1,488		1,451
Net change in short-term investments	(392)		521		121
Net derivative instruments settlements	(283)		(470)		(280)
Acquisition of subsidiaries (net of cash acquired)	(766)		(977)		(98)
Capital contribution to subsidiary					(90)
Other	(266)		(389)		(522)
Net cash flows used for investing activities	(2,333)		(4,440)		(3,491)
Dividends paid on Common Shares					0
Common Shares repurchased	(1,429)		(287)		(11)
Proceeds from issuance of long-term debt	0
Proceeds from issuance of short-term debt	1,978		2,572		2,803
Repayments of Long-term Debt	(1)
Repayments of Short-term Debt	(1,977)		(2,572)		(2,653)
Net proceeds from (repayments) issuance of short-term debt			0
Proceeds from share-based compensation plans	127		121		92
Advances from (to) affiliates	38				(5)
Capital contribution from subsidiary	258		1,230		352
Net proceeds from (payments to) affiliated notional cash pooling programs			0	[2]	0	[1]
Dividends to parent company	(674)		(825)		(750)
Other	194		113
Net cash flows (used for) from financing activities	(1,486)		352		(172)
Effect of foreign currency rate changes on cash and cash equivalents	(139)		(7)		(5)
Net increase (decrease) in cash	461		(111)		208
Cash – beginning of year	748	[2],[3],[4]	859	[1],[2]	651	[1]
Cash – end of year	1,209	[3],[5]	748	[2],[3],[4]	859	[1],[2]
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	(674)		(825)		(750)
Purchases of fixed maturities available for sale	263		106		115
Purchases of fixed maturities held to maturity					0
Purchases of equity securities					0
Sales of fixed maturities available for sale	(268)		(106)		(115)
Sales of equity securities					0
Maturities and redemptions of fixed maturities available for sale					0
Maturities and redemptions of fixed maturities held to maturity					0
Net change in short-term investments	5		0		0
Net derivative instruments settlements					0
Acquisition of subsidiaries (net of cash acquired)					0
Capital contribution to subsidiary	258		1,230		442
Other					0
Net cash flows used for investing activities	258		1,230		442
Dividends paid on Common Shares					0
Common Shares repurchased					0
Proceeds from issuance of short-term debt					0
Net proceeds from (repayments) issuance of short-term debt			0
Net proceeds from issuances of long-term debt	0
Proceeds from share-based compensation plans					0
Advances from (to) affiliates	0				0
Capital contribution from subsidiary	(258)		(1,230)		(442)
Net proceeds from (payments to) affiliated notional cash pooling programs	(370)	[3]	164	[2]	(201)	[1]
Dividends to parent company	674		825		750
Net cash flows (used for) from financing activities	46		(241)		107
Effect of foreign currency rate changes on cash and cash equivalents					0
Net increase (decrease) in cash	(370)		164		(201)
Cash – beginning of year	(185)	[2],[3],[4]	(349)	[1],[2]	(148)	[1]
Cash – end of year	$ (555)	[3],[5]	$ (185)	[2],[3],[4]	$ (349)	[1],[2]

[1] (1)ACE maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2012 and 2011, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[2] (1)ACE maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2013 and 2012, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[3] (1) ACE maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2014 and 2013, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[4] (1) ACE maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2013, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[5] (1) ACE maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2014, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.