Business Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011 cubicFeet Mi	Sep. 30, 2010	Sep. 30, 2011 cubicFeet Mi	Sep. 30, 2010	Dec. 31, 2009
Segment Reporting Information [Line Items]
Revenues	$ 3,438	$ 3,701	$ 10,648	$ 10,900
Income (loss) before income tax and noncontrolling interests	439	258	1,751	1,957
Net income (loss)	162	36	796	822
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	(27)	62	15	94
Investment gains (losses) included in net income (loss) - Loews	(15)	37	9	49
Income from continuing operations	162	56	796	841
Discontinued operations, net		(20)		(19)
Number of offshore drilling rigs	46		46
Number of countries where drilling rigs are located	11		11
HighMount's total proved reserves located in Michigan and Alabama					17.00%
Miles of natural gas pipeline	14,200		14,200
Total number of parent hotels owned	18		18
Number of parent hotels in the United States	16		16
Number of parent hotels in Canada	2		2
CNA Specialty [Member]
Segment Reporting Information [Line Items]
Revenues	874	899	2,640	2,640
Income (loss) before income tax and noncontrolling interests	124	250	529	768
Net income (loss)	70	139	299	432
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	(8)	15	7	60
Investment gains (losses) included in net income (loss) - Loews	(5)	8	4	35
CNA Commercial [Member]
Segment Reporting Information [Line Items]
Revenues	962	1,072	3,040	3,132
Income (loss) before income tax and noncontrolling interests	80	189	362	542
Net income (loss)	33	110	202	312
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	(15)	21	13	30
Investment gains (losses) included in net income (loss) - Loews	(8)	13	8	13
Life And Group Non-Core [Member]
Segment Reporting Information [Line Items]
Revenues	334	351	993	992
Income (loss) before income tax and noncontrolling interests	(43)	(59)	(136)	(125)
Net income (loss)	(15)	(38)	(50)	(58)
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	(4)	20	(7)	15
Investment gains (losses) included in net income (loss) - Loews	(2)	11	(4)	7
Other Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	6	41	29	147
Income (loss) before income tax and noncontrolling interests	(34)	(546)	(110)	(542)
Net income (loss)	(19)	(314)	(65)	(306)
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests		6	1	20
Investment gains (losses) included in net income (loss) - Loews		5	1	13
Total CNA Financial [Member]
Segment Reporting Information [Line Items]
Revenues	2,176	2,363	6,702	6,911
Income (loss) before income tax and noncontrolling interests	127	(166)	645	643
Net income (loss)	69	(103)	386	380
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	(27)	62	14	125
Investment gains (losses) included in net income (loss) - Loews	(15)	37	9	68
Diamond Offshore [Member]
Segment Reporting Information [Line Items]
Revenues	881	833	2,582	2,518
Income (loss) before income tax and noncontrolling interests	335	298	974	1,023
Net income (loss)	121	93	363	333
HighMount [Member]
Segment Reporting Information [Line Items]
Revenues	95	98	297	351
Income (loss) before income tax and noncontrolling interests	25	30	78	105
Net income (loss)	16	19	50	56
Boardwalk Pipeline [Member]
Segment Reporting Information [Line Items]
Revenues	269	264	843	821
Income (loss) before income tax and noncontrolling interests	46	55	141	196
Net income (loss)	18	21	56	80
Loews Hotels [Member]
Segment Reporting Information [Line Items]
Revenues	82	74	251	230
Income (loss) before income tax and noncontrolling interests	(1)	(1)	13	4
Net income (loss)		(2)	8	1
Corporate And Other [Member]
Segment Reporting Information [Line Items]
Revenues	(65)	69	(27)	69
Income (loss) before income tax and noncontrolling interests	(93)	42	(100)	(14)
Net income (loss)	(62)	28	(67)	(9)
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests			1	(31)
Investment gains (losses) included in net income (loss) - Loews				$ (19)