Schedule II (STATEMENTS OF CASH FLOWS - Parent Company Only) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities	$ 3,995		$ 3,470		$ 3,546
Purchases of fixed maturities available for sale	(23,455)		(23,823)		(29,985)
Sales of fixed maturities available for sale	14,321		17,176		23,096
Net derivative instruments settlements	(281)		(67)		(109)
Advances (to) from affiliates
Other	555		482		333
Net cash flows from (used for) investing activities	(3,439)		(3,036)		(4,181)
Dividends paid on Common Shares	(815)		(459)		(435)
Proceeds from share-based compensation plans	126		139		62
Net cash flows from (used for) financing activities	(550)		(565)		732
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]
Parent Company Only
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities	781		762		(176)
Purchases of fixed maturities available for sale	0		0		(1)
Sales of fixed maturities available for sale	0		9		0
Net derivative instruments settlements	(1)		(3)		(3)
Capital contributions to subsidiaries	0		(385)		(290)
Advances (to) from affiliates	(2)		41		851
Net cash flows from (used for) investing activities	(3)		(338)		557
Dividends paid on Common Shares	(815)		(459)		(435)
Net proceeds from issuance (repayment) of short-term debt	0		(300)		300
Proceeds from share-based compensation plans	34		133		63
Net cash flows from (used for) financing activities	(781)		(626)		(72)
Net increase (decrease) in cash	(3)		(202)		309
Cash - beginning of period	106		308	[2]	(1)	[1]
Cash - end of period	$ 103	[3],[4]	$ 106		$ 308	[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, 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.