Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Statement Of Operations and Comprehensive Income) (Detail) - USD ($) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014		Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written										$ 17,713	$ 17,799	$ 17,025
Net premiums earned	$ 4,207	$ 4,719	$ 4,360	$ 3,927		$ 4,370	$ 4,754	$ 4,332	$ 3,970	17,213	17,426	16,613
Net investment income	532	549	562	551		577	566	556	553	2,194	2,252	2,144
Net realized gains (losses) including OTTI	(60)	(397)	126	(89)		(210)	(120)	(73)	(104)	(420)	(507)	504
Losses and loss expenses	2,302	2,643	2,417	2,122		2,416	2,684	2,388	2,161	9,484	9,649	9,348
Policy benefits	159	89	153	142		134	125	144	114	543	517	515
Policy acquisition costs and administrative expenses										5,211	5,320	4,870
Interest (income) expense										300	280	275
Other (income) expense										(51)	(190)	(80)
Amortization of Intangible Assets										171	108	95
Chubb integration expenses										33	0	0
Income tax expense										462	634	480
Net income (loss)	$ 683	$ 528	$ 942	$ 681	[1]	$ 555	$ 785	$ 779	$ 734	2,834	2,853	3,758
Comprehensive income										908	2,892	2,023
ACE limited (Parent Gurantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written												0
Net premiums earned												0
Net investment income										3	2	2
Equity in earnings of subsidiaries										2,673	2,707	3,580
Net realized gains (losses) including OTTI										0	0	0
Losses and loss expenses												0
Policy benefits												0
Policy acquisition costs and administrative expenses										63	78	60
Interest (income) expense										(32)	(35)	(32)
Other (income) expense										(208)	(201)	(221)
Amortization of Intangible Assets										0	0	0
Chubb integration expenses										3
Income tax expense										16	14	17
Net income (loss)										2,834	2,853	3,758
Comprehensive income										908	2,892	2,023
ACE INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written										0	0	0
Net premiums earned										0	0	0
Net investment income										4	2	3
Equity in earnings of subsidiaries										1,038	791	942
Net realized gains (losses) including OTTI										(9)	53	(2)
Losses and loss expenses										0	0	0
Policy benefits										0	0	0
Policy acquisition costs and administrative expenses										28	26	19
Interest (income) expense										302	277	270
Other (income) expense										(4)	27	27
Amortization of Intangible Assets										0	0	0
Chubb integration expenses										29
Income tax expense										(349)	(94)	(108)
Net income (loss)										1,027	610	735
Comprehensive income										(192)	583	(230)
Other ACE Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written												17,025
Net premiums earned												16,613
Net investment income												2,139
Equity in earnings of subsidiaries												0
Net realized gains (losses) including OTTI												506
Losses and loss expenses												9,348
Policy benefits												515
Policy acquisition costs and administrative expenses												4,791
Interest (income) expense												37
Other (income) expense												114
Income tax expense												571
Net income (loss)												3,787
Comprehensive income												2,051
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written												0
Net premiums earned												0
Net investment income												0
Equity in earnings of subsidiaries										(3,711)	(3,498)	(4,522)
Net realized gains (losses) including OTTI												0
Losses and loss expenses												0
Policy benefits												0
Policy acquisition costs and administrative expenses												0
Interest (income) expense												0
Other (income) expense												0
Amortization of Intangible Assets										0	0	0
Chubb integration expenses										0
Income tax expense												0
Net income (loss)										(3,711)	(3,498)	(4,522)
Comprehensive income										(565)	(3,509)	(1,821)
Other ACE Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written										17,713	17,799
Net premiums earned										17,213	17,426
Net investment income										2,187	2,248
Net realized gains (losses) including OTTI										(411)	(560)
Losses and loss expenses										9,484	9,649
Policy benefits										543	517
Policy acquisition costs and administrative expenses										5,120	5,216
Interest (income) expense										30	38
Other (income) expense										161	(16)
Amortization of Intangible Assets										171	108	$ 95
Chubb integration expenses										1
Income tax expense										795	714
Net income (loss)										2,684	2,888
Comprehensive income										$ 757	$ 2,926

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