Consolidated Statements Of Operations And Comprehensive Income (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenues
Net premiums written	$ 4,343	$ 3,295	$ 11,742	$ 10,286
Change in unearned premiums	147	127	(186)	(354)
Net premiums earned	4,490	3,422	11,556	9,932
Net investment income	564	516	1,677	1,538
Net realized gains (losses):
Other-than-temporary impairment (OTTI) losses gross	(31)	(39)	(45)	(120)
Portion of OTTI losses recognized in other comprehensive income (OCI)	11	20	13	65
Net OTTI losses recognized in income	(20)	(19)	(32)	(55)
Net realized gains (losses) excluding OTTI losses	(740)	(31)	(846)	182
Total net realized gains (losses)	(760)	(50)	(878)	127
Total revenues	4,294	3,888	12,355	11,597
Expenses
Losses and loss expenses	2,745	1,887	7,234	5,608
Policy benefits	83	93	282	267
Policy acquisition costs	666	607	1,825	1,697
Administrative expenses	517	433	1,526	1,356
Interest expense	62	58	187	162
Other (income) expense	87	(25)	82	(26)
Total expenses	4,160	3,053	11,136	9,064
Income before income tax	134	835	1,219	2,533
Income tax expense	165	160	384	426
Net income (loss)	(31)	675	835	2,107
Other comprehensive income (loss)
Unrealized appreciation	22	953	391	2,023
Reclassification adjustment for net realized gains included in net income	(18)	(120)	(152)	(346)
Subtotal	4	833	239	1,677
Change in:
Cumulative translation adjustment	(152)	186	149	(73)
Pension liability	3	(6)	(2)	2
Other comprehensive income, before income tax	(145)	1,013	386	1,606
Income tax expense related to OCI items	(5)	(197)	(141)	(319)
Other comprehensive income (loss)	(150)	816	245	1,287
Comprehensive income (loss)	$ (181)	$ 1,491	$ 1,080	$ 3,394
Earnings per share
Basic earnings per share	$ (0.09)	$ 1.98	$ 2.47	$ 6.21
Diluted earnings per share	$ (0.09)	$ 1.97	$ 2.45	$ 6.18