Consolidated Statements Of Operations and Comprehensive Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Document Fiscal Year Focus	2013
Revenues
Net premiums written	$ 3,798	$ 3,572
Change in unearned premiums	(225)	(191)
Net premiums earned	3,573	3,381
Net investment income	531	544
Net realized gains (losses):
Other-than-temporary impairment (OTTI) losses gross	(3)	(10)
Portion of OTTI losses recognized in other comprehensive income (OCI)	0	0
Net OTTI losses recognized in income	(3)	(10)
Net realized gains (losses) excluding OTTI losses	209	270
Total net realized gains (losses)	206	260
Total revenues	4,310	4,185
Expenses
Losses and loss expenses	1,926	1,804
Policy benefits	131	147
Policy acquisition costs	614	582
Administrative expenses	514	510
Interest expense	60	62
Other (income) expense	(10)	(3)
Total expenses	3,235	3,102
Income before income tax	1,075	1,083
Income tax expense (includes $5 Income tax expesne from reclassification of unrealized gains in 2013)	122	110
Net income	953	973
Other comprehensive income (loss)
Unrealized appreciation	(116)	325
Reclassification adjustment for net realized gains (losses) included in net income	(35)	(33)
Other comprehensive income	(151)	292
Change in:
Cumulative translation adjustment	(211)	88
Pension liability	22	(2)
Other comprehensive income, before income tax	(340)	378
Income tax expense related to OCI items	103	(80)
Other comprehensive income	(237)	298
Comprehensive income	$ 716	$ 1,271
Earnings per share
Basic earnings per share (US$ per share)	$ 2.80	$ 2.87
Diluted earnings per share (US$ per share)	$ 2.77	$ 2.84