Business Segments (Consolidated Revenues and Income (Loss) Attributable to Loews Corporation by Business Segment) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Revenues	$ 3,715	$ 3,438	$ 10,847	$ 10,648
Income (loss) before income tax and noncontrolling interests	409	439	1,364	1,744
Net income (loss) - Loews	177	162	600	791
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	7	(27)	59	15
Investment gains (losses) included in net income (loss)	4	(15)	35	9
CNA Specialty [Member]
Segment Reporting Information [Line Items]
Revenues	957	874	2,798	2,640
Income (loss) before income tax and noncontrolling interests	214	123	589	527
Net income (loss) - Loews	122	69	347	297
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	2	(8)	18	7
Investment gains (losses) included in net income (loss)	1	(5)	11	4
CNA Commercial [Member]
Segment Reporting Information [Line Items]
Revenues	1,091	962	3,163	3,040
Income (loss) before income tax and noncontrolling interests	193	81	519	357
Net income (loss) - Loews	119	34	309	199
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	10	(15)	34	13
Investment gains (losses) included in net income (loss)	6	(8)	20	8
Life And Group Non-Core [Member]
Segment Reporting Information [Line Items]
Revenues	340	334	1,050	993
Income (loss) before income tax and noncontrolling interests	(60)	(43)	(111)	(136)
Net income (loss) - Loews	(21)	(15)	(26)	(50)
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	(3)	(4)	14	(7)
Investment gains (losses) included in net income (loss)	(2)	(2)	8	(4)
Other Segments[Member]
Segment Reporting Information [Line Items]
Revenues	77	6	101	29
Income (loss) before income tax and noncontrolling interests	(33)	(34)	(84)	(110)
Net income (loss) - Loews	(20)	(19)	(53)	(65)
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	(1)		(4)	1
Investment gains (losses) included in net income (loss)			(2)	1
Total CNA Financial [Member]
Segment Reporting Information [Line Items]
Revenues	2,465	2,176	7,112	6,702
Income (loss) before income tax and noncontrolling interests	314	127	913	638
Net income (loss) - Loews	200	69	577	381
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	8	(27)	62	14
Investment gains (losses) included in net income (loss)	5	(15)	37	9
Diamond Offshore [Member]
Segment Reporting Information [Line Items]
Revenues	730	881	2,319	2,582
Income (loss) before income tax and noncontrolling interests	234	335	732	974
Net income (loss) - Loews	83	121	264	363
Boardwalk Pipeline [Member]
Segment Reporting Information [Line Items]
Revenues	271	269	862	843
Income (loss) before income tax and noncontrolling interests	58	46	216	141
Net income (loss) - Loews	20	18	80	56
HighMount [Member]
Segment Reporting Information [Line Items]
Revenues	74	95	219	297
Income (loss) before income tax and noncontrolling interests	(248)	25	(499)	78
Net income (loss) - Loews	(158)	16	(319)	50
Loews Hotels [Member]
Segment Reporting Information [Line Items]
Revenues	98	82	272	251
Income (loss) before income tax and noncontrolling interests	(1)	(1)	17	13
Net income (loss) - Loews	(1)		9	8
Corporate And Other [Member]
Segment Reporting Information [Line Items]
Revenues	77	(65)	63	(27)
Income (loss) before income tax and noncontrolling interests	52	(93)	(15)	(100)
Net income (loss) - Loews	33	(62)	(11)	(67)
Investment gains (losses) included in revenues and income (loss) before income tax and noncontrolling interests	(1)		(3)	1
Investment gains (losses) included in net income (loss)	$ (1)		$ (2)