Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2012

Quarterly Financial Data [Abstract]

Schedule of quarterly financial information

Quarterly Financial Data

2012
(In millions, except per share data)	First		Second		Third		Fourth			Full Year
Revenues	$	2,401	$	2,246	$	2,466	$	2,434		$	9,547
Net income attributable to CNA	$	250	$	166	$	221	$	(9	)	$	628
Basic and diluted earnings (loss) per share attributable to CNA common stockholders (a)	$	0.93	$	0.62	$	0.82	$	(0.03	)	$	2.33

2011
(In millions, except per share data)	First			Second			Third			Fourth			Full Year
Revenues	$	2,315		$	2,198		$	2,175		$	2,261		$	8,949
Income (loss) from continuing operations	230			129			76			194			629
Income (loss) from discontinued operations, net of income tax (expense) benefit	(1		)	—			—			—			(1		)
Net (income) loss attributable to noncontrolling interests	(9		)	(5		)	(1		)	(1		)	(16		)
Net income (loss) attributable to CNA	$	220		$	124		$	75		$	193		$	612
Basic and Diluted Earnings (Loss) Per Share Attributable to CNA Common Stockholders
Income (loss) from continuing operations attributable to CNA common stockholders	$	0.82		$	0.46		$	0.28		$	0.71		$	2.27
Income (loss) from discontinued operations attributable to CNA common stockholders	—			—			—			—			—
Basic and diluted earnings (loss) per share attributable to CNA common stockholders	$	0.82		$	0.46		$	0.28		$	0.71		$	2.27

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(a) Due to the averaging of shares, quarterly earnings per share do not add to the total for the full year.