Consolidating Financial Information - Consolidating Statement of Income Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Condensed Financial Statements, Captions [Line Items]
Insurance premiums	$ 1,810		$ 1,825		$ 5,427		$ 5,389
Net investment income	451		605		1,625		1,739
Investment gains	37	[1]	2	[1]	65	[1]	7	[1]
Contract drilling revenues	728		691		2,063		2,136
Other Revenues	497		474		1,624		1,560
Total					10,804		10,831
Expenses:
Insurance claims and policyholders' benefits	1,354		1,378		4,241		4,259
Amortization of deferred acquisition costs	332		341		996		1,004
Contract drilling expenses	400		420		1,165		1,164
Other operating expenses	977		777		2,634		2,309
Interest	121		105		369		316
Total	3,184		3,021		9,405		9,052
Income before income tax	339		576		1,399		1,779
Income tax (expense) benefit	(99)		(155)		(347)		(478)
Income from continuing operations	240		421		1,052		1,301
Discontinued operations, net	29		(37)		(384)		(107)
Net income	269		384		668		1,194
Amounts attributable to noncontrolling interests	(61)		(102)		(285)		(401)
Net income attributable to Loews Corporation					383		793
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Intercompany interest and dividends					(647)		(547)
Total					(647)		(547)
Expenses:
Income before income tax					(647)		(547)
Income from continuing operations					(647)		(547)
Net income					(647)		(547)
Net income attributable to Loews Corporation					(647)		(547)
CNA Financial [Member] | Operating Segments [Member]
Condensed Financial Statements, Captions [Line Items]
Insurance premiums					5,427		5,389
Net investment income					1,556		1,680
Investment gains					65		7
Other Revenues					266		287
Total					7,314		7,363
Expenses:
Insurance claims and policyholders' benefits					4,241		4,259
Amortization of deferred acquisition costs					996		1,004
Other operating expenses					978		979
Interest					138		125
Total					6,353		6,367
Income before income tax					961		996
Income tax (expense) benefit					(268)		(290)
Income from continuing operations					693		706
Discontinued operations, net					(197)		14
Net income					496		720
Amounts attributable to noncontrolling interests					(50)		(72)
Net income attributable to Loews Corporation					446		648
Diamond Offshore [Member] | Operating Segments [Member]
Condensed Financial Statements, Captions [Line Items]
Net investment income					1		1
Contract drilling revenues					2,063		2,136
Other Revenues					84		61
Total					2,148		2,198
Expenses:
Contract drilling expenses					1,165		1,164
Other operating expenses					575		423
Interest					46		18
Total					1,786		1,605
Income before income tax					362		593
Income tax (expense) benefit					(84)		(154)
Income from continuing operations					278		439
Net income					278		439
Amounts attributable to noncontrolling interests					(142)		(226)
Net income attributable to Loews Corporation					136		213
Boardwalk Pipeline [Member] | Operating Segments [Member]
Condensed Financial Statements, Captions [Line Items]
Other Revenues					931		921
Total					931		921
Expenses:
Other operating expenses					705		573
Interest					121		122
Total					826		695
Income before income tax					105		226
Income tax (expense) benefit					(5)		(49)
Income from continuing operations					100		177
Net income					100		177
Amounts attributable to noncontrolling interests					(93)		(103)
Net income attributable to Loews Corporation					7		74
Loews Hotels [Member] | Operating Segments [Member]
Condensed Financial Statements, Captions [Line Items]
Other Revenues					343		290
Total					343		290
Expenses:
Other operating expenses					320		282
Interest					9		8
Total					329		290
Income before income tax					14
Income tax (expense) benefit					(6)		2
Income from continuing operations					8		2
Net income					8		2
Net income attributable to Loews Corporation					8		2
Corporate and Other [Member]
Condensed Financial Statements, Captions [Line Items]
Net investment income					68		58
Intercompany interest and dividends					647		547
Other Revenues							1
Total					715		606
Expenses:
Other operating expenses					56		52
Interest					55		43
Total					111		95
Income before income tax					604		511
Income tax (expense) benefit					16		13
Income from continuing operations					620		524
Discontinued operations, net					(187)		(121)
Net income					433		403
Net income attributable to Loews Corporation					$ 433		$ 403

[1] (a) Includes gross realized gains of $52, $50, $130 and $129 and gross realized losses of $16, $50, $70 and $124 on available-for-sale securities for the three and nine months ended September 30, 2014 and 2013.