Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Changes in:
Net unrealized gains (losses) on investments with other-than-temporary impairments	$ 3	$ (1)	$ (37)	$ (39)
Change in net unrealized gains (losses) on other investments	121	300	339	322
Net unrealized gains (losses) on investments	118	301	376	361
Foreign currency translation adjustment	(17)	5	4	30
Pension and postretirement benefits	3	1	9	2
Net unrealized gains (losses) on discontinued operations and other				1
Allocation to participating policyholders	(1)	(1)	(2)	(1)
Other comprehensive income (loss), net of tax	103	306	387	393
Net income (loss)	166	129	416	358
Comprehensive income (loss)	269	435	803	751
NetUnrealized(Gains)LossesOnInvestmentsAttributableToNoncontrollingInterests		10		8
Net (income) loss attributable to noncontrolling interests		(5)		(14)
Comprehensive (income) loss attributable to noncontrolling interests		15		22
Total comprehensive income (loss) attributable to CNA	$ 269	$ 420	$ 803	$ 729