Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues
Net earned premiums	$ 6,882	$ 6,603	$ 6,515
Net investment income	2,282	2,054	2,316
Net realized investment gains (losses), net of participating policyholders’ interests:
Other-than-temporary impairment losses	(129)	(175)	(254)
Portion of other-than-temporary impairments recognized in Other comprehensive income (loss)	(25)	(41)	22
Net other-than-temporary impairment losses recognized in earnings	(154)	(216)	(232)
Other net realized investment gains (losses)	217	214	318
Net realized investment gains (losses), net of participating policyholders’ interests	63	(2)	86
Other revenues	320	294	292
Total revenues	9,547	8,949	9,209
Claims, Benefits and Expenses
Insurance claims and policyholders’ benefits	5,896	5,489	4,985
Amortization of deferred acquisition costs	1,274	1,176	1,168
Other operating expenses	1,335	1,238	1,787
Interest	170	175	157
Total claims, benefits and expenses	8,675	8,078	8,097
Income (loss) from continuing operations before income tax	872	871	1,112
Income tax (expense) benefit	(244)	(242)	(332)
Income (loss) from continuing operations	628	629	780
Income (loss) from discontinued operations, net of income tax (expense) benefit of -, $0 and $0		(1)	(21)
Net income (loss)	628	628	759
Net (income) loss attributable to noncontrolling interests		(16)	(68)
Net income (loss) attributable to CNA	628	612	691
Income (Loss) Attributable to CNA Common Stockholders
Income (loss) from continuing operations attributable to CNA	628	613	712
Dividends on 2008 Senior Preferred			(76)
Income (loss) from continuing operations attributable to CNA common stockholders	628	613	636
Income (loss) from discontinued operations attributable to CNA common stockholders		(1)	(21)
Income (loss) attributable to CNA common stockholders	$ 628	$ 612	$ 615
Basic and Diluted Earnings (Loss) Per Share Attributable to CNA Common Stockholders
Income (loss) from continuing operations attributable to CNA common stockholders	$ 2.33	$ 2.27	$ 2.36
Income (loss) from discontinued operations attributable to CNA common stockholders			$ (0.08)
Basic and diluted earnings (loss) per share attributable to CNA common stockholders	$ 2.33	$ 2.27	$ 2.28
Dividends per share	$ 0.60	$ 0.40
Weighted Average Outstanding Common Stock and Common Stock Equivalents
Basic	269.4	269.3	269.1
Diluted	269.8	269.6	269.5