Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cumulative effect adjustment of after tax and noncontrolling interests			$ 109,000,000
Net unrealized gains on investments included in "AOCI"	659,000,000	135,000,000
Shadow Adjustments, net of participating policyholders' interest	524,000,000	135,000,000
Initial collateral deposit as a percentage of the fair value of the securities loaned	100.00%
Minimum interest rate used to calculate reserves for long term care products	5.00%	6.00%
Maximum interest rate used to calculate reserves for long term care products	7.50%	7.60%
Interest rates for payout annuity contracts, minimum	5.40%	2.80%
Interest rates for payout annuity contracts, maximum	7.50%	10.20%
Increase in insurance reserves	166,000,000
Liability balance for guaranty fund	152,000,000	160,000,000
Related assets for premium tax offsets	2,000,000	3,000,000
Deferred acquisition costs	412,000,000
Billed receivables % of total reinsurance receivables	5.00%
Investments in life settlement contracts	117,000,000
Tax benefit of a qualifying position is the largest amount of tax benefit threshold	50.00%
Recognized compensation expense	12,000,000	12,000,000	12,000,000
Potential shares attributable to exercises included in diluted EPS calculation	0.8	0.8	0.6
Shares excluded from diluted EPS calculation	2.0	2.4	3.4
Foreign currency transaction losses	5,000,000	18,000,000	2,000,000
Cash payments made for interest on long term debt, net of capitalized interest	526,000,000	494,000,000	442,000,000
Cash payments for federal, foreign, state and local income taxes amount	322,000,000	378,000,000	219,000,000
Previously accrued capital expenditures included in Investment activities		51,000,000	235,000,000
Investing activities excluding capital expenditures	14,000,000
Estimated decrease to shareholders' equity upon adoption of new accounting pronouncement	63,000,000
Boardwalk Pipeline Partners, LP [Member]
Ownership percentage in subsidiary	61.00%
CNA Financial Corporation [Member]
Ownership percentage in subsidiary	90.00%
Anticipated amounts due from insureds related to losses under deductible policies	1,400,000,000	1,400,000,000
Minimum interest rate used in determining present value of obligations of structured settlements unfunded by annuities	5.50%	4.60%
Maximum interest rate used in determining present value of obligations of structured settlements unfunded by annuities	8.00%	7.50%
Discounted reserves for unfunded structured settlements	632,000,000	713,000,000
Discounted reserves for unfunded structured settlements, net of discount	1,100,000,000	1,100,000,000
Minimum interest rate used to discount workers' compensation lifetime claim reserves and accident and health claim reserves	3.00%	3.00%
Maximum interest rate used to discount workers' compensation lifetime claim reserves and accident and health claim reserves	6.50%	6.50%
Discounted reserves for workers' compensation lifetime claims and accident and health claims	2,100,000,000	1,900,000,000
Discounted reserves for workers' compensation lifetime claims and accident and health claims, net of discount	520,000,000	487,000,000
Deposit assets	18,000,000	23,000,000
Deposit liabilities	123,000,000	114,000,000
Investments in life settlement contracts	117,000,000	129,000,000
Increase in fair value recognized on life settlement contracts	5,000,000	10,000,000	10,000,000
Gain recognized on matured life settlement contracts	28,000,000	19,000,000	24,000,000
Additional policyholders funds liability increase (decrease)	$ 18,000,000	$ (24,000,000)	$ (42,000,000)
Diamond Offshore Drilling, Inc. [Member]
Ownership percentage in subsidiary	50.40%
HighMount Exploration & Production LLC [Member]
Ownership percentage in subsidiary	100.00%
Percentage of total proved reserves	4.20%
Loews Hotels Holding Corporation [Member]
Ownership percentage in subsidiary	100.00%
Minimum [Member]
Percentage equity method investments in associated companies	20.00%
Maximum [Member]
Percentage equity method investments in associated companies	50.00%