Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Statement Of Operations and Comprehensive Income) (Detail) (USD $) In Millions, unless otherwise specified	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, 2014	Dec. 31, 2013	Dec. 31, 2012
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written										$ 17,799	$ 17,025	$ 16,075
Net premiums earned	4,370	4,754	4,332	3,970		4,363	4,610	4,067	3,573	17,426	16,613	15,677
Net investment income	577	566	556	553		557	522	534	531	2,252	2,144	2,181
Net realized gains (losses) including OTTI	(210)	(120)	(73)	(104)		154	40	104	206	(507)	504	78
Losses and loss expenses	2,416	2,684	2,388	2,161		2,517	2,655	2,250	1,926	9,649	9,348	9,653
Policy benefits	134	125	144	114		136	138	110	131	517	515	521
Policy acquisition costs and administrative expenses										5,320	4,870	4,542
Interest (income) expense										280	275	250
Other (income) expense										(82)	15	(6)
Income tax expense										634	480	270
Net income (loss)	555	785	779	734	[1]	998	916	891	953	2,853	3,758	2,706
Comprehensive income										2,892	2,023	3,682
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										2	2	1
Equity in earnings of subsidiaries										2,707	3,580	2,590
Net realized gains (losses) including OTTI										0	0	17
Losses and loss expenses												0
Policy benefits												0
Policy acquisition costs and administrative expenses										78	60	62
Interest (income) expense										(35)	(32)	(33)
Other (income) expense										(201)	(221)	(137)
Income tax expense										14	17	10
Net income (loss)										2,853	3,758	2,706
Comprehensive income										2,892	2,023	3,682
ACE INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written												0
Net premiums earned												0
Net investment income												3
Equity in earnings of subsidiaries												911
Net realized gains (losses) including OTTI												0
Losses and loss expenses												0
Policy benefits												0
Policy acquisition costs and administrative expenses												28
Interest (income) expense												235
Other (income) expense												9
Income tax expense												(110)
Net income (loss)												752
Comprehensive income												1,209
Other ACE Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written												16,075
Net premiums earned												15,677
Net investment income												2,177
Equity in earnings of subsidiaries												0
Net realized gains (losses) including OTTI												61
Losses and loss expenses												9,653
Policy benefits												521
Policy acquisition costs and administrative expenses												4,452
Interest (income) expense												48
Other (income) expense												122
Income tax expense												370
Net income (loss)												2,749
Comprehensive income												3,724
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										(3,498)	(4,522)	(3,501)
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
Income tax expense												0
Net income (loss)										(3,498)	(4,522)	(3,501)
Comprehensive income										(3,509)	(1,821)	(4,933)
ACE INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net investment income										2	3
Equity in earnings of subsidiaries										791	942
Net realized gains (losses) including OTTI										53	(2)
Policy acquisition costs and administrative expenses										26	19
Interest (income) expense										277	270
Other (income) expense										27	27
Income tax expense										(94)	(108)
Net income (loss)										610	735
Comprehensive income										583	(230)
Other ACE Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written										17,799	17,025
Net premiums earned										17,426	16,613
Net investment income										2,248	2,139
Net realized gains (losses) including OTTI										(560)	506
Losses and loss expenses										9,649	9,348
Policy benefits										517	515
Policy acquisition costs and administrative expenses										5,216	4,791
Interest (income) expense										38	37
Other (income) expense										92	209
Income tax expense										714	571
Net income (loss)										2,888	3,787
Comprehensive income										$ 2,926	$ 2,051

[1] (1) Net income for the three months ended December 31, 2014 includes $89 million of net charges related to income taxes to correct prior periods. Such amounts are not material to any period presented.