Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Cash flows from operating activities
Net income	$ 2,706		$ 1,540		$ 3,085
Adjustments to reconcile net income to net cash flows from operating activities
Net realized (gains) losses	(78)		795		(432)
Amortization of premiums/discounts on fixed maturities	220		152		145
Deferred income taxes	(7)		15		110
Unpaid losses and loss expenses	203		43		(360)
Unearned premiums	522		9		262
Future policy benefits	158		78		48
Insurance and reinsurance balances payable	(151)		216		(172)
Accounts payable, accrued expenses, and other liabilities	(42)		39		130
Income taxes payable	(167)		39		10
Insurance and reinsurance balances receivable	335		(217)		50
Reinsurance recoverable on losses and loss expenses	372		531		626
Reinsurance recoverable on policy benefits	52		25		49
Deferred policy acquisition costs	(340)		(122)		(170)
Prepaid reinsurance premiums	(123)		(34)		(13)
Other	335		361		178
Net cash flows from operating activities	3,995		3,470		3,546
Cash flows from investing activities
Purchases of fixed maturities available for sale	(23,455)		(23,823)		(29,985)
Purchases of to be announced mortgage-backed securities	(389)		(755)		(1,271)
Purchases of fixed maturities held to maturity	(388)		(340)		(616)
Purchases of equity securities	(135)		(309)		(794)
Sales of fixed maturities available for sale	14,321		17,176		23,096
Sales of to be announced mortgage-backed securities	448		795		1,183
Sales of equity securities	119		376		774
Maturities and redemptions of fixed maturities available for sale	5,523		3,720		3,660
Maturities and redemptions of fixed maturities held to maturity	1,451		1,279		1,353
Net derivative instruments settlements	(281)		(67)		(109)
Acquisition of subsidiaries (net of cash acquired of $8, $91 and $80)	(98)		(606)		(1,139)
Other	(555)		(482)		(333)
Net cash flows from (used for) investing activities	(3,439)		(3,036)		(4,181)
Cash flows from financing activities
Dividends paid on Common Shares	(815)		(459)		(435)
Common Shares repurchased	(11)		(195)		(235)
Proceeds from issuance of short-term debt	2,933		5,238		1,300
Repayment of short-term debt	(2,783)		(5,288)		(159)
Proceeds from issuances of long-term debt					699
Repayments of Long-term Debt					(500)
Proceeds from share-based compensation plans	126		139		62
Net cash flows from (used for) financing activities	(550)		(565)		732
Effect of foreign currency rate changes on cash and cash equivalents	(5)		(27)		6
Net increase (decrease) in cash	1		(158)		103
Cash - beginning of period	614		772	[1],[2]	669	[1]
Cash - end of period	615	[3],[4]	614		772	[1],[2]
Supplemental cash flow information
Taxes paid	438		460		434
Interest paid	$ 240		$ 234		$ 204

[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, 2010 and 2009, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[2] 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, 2010, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

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

[4] 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, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.