Consolidating Financial Information - Consolidating Statement of Income Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Insurance premiums	$ 6,921	$ 7,212	$ 7,271
Net investment income	1,866	2,163	2,425
Investment gains (losses)	(71)	54	16
Contract drilling revenues	2,360	2,737	2,844
Other revenues	2,339	2,159	2,057
Total	13,415	14,325	14,613
Expenses:
Insurance claims and policyholders' benefits	5,384	5,591	5,806
Amortization of deferred acquisition costs	1,540	1,317	1,362
Contract drilling expenses	1,228	1,524	1,573
Other operating expenses	4,499	3,585	3,170
Interest	520	498	425
Total	13,171	12,515	12,336
Income (loss) before income tax	244	1,810	2,277
Income tax (expense) benefit	43	(457)	(656)
Income from continuing operations	287	1,353	1,621
Discontinued operations, net		(391)	(552)
Net income	287	962	1,069
Amounts attributable to noncontrolling interests	(27)	(371)	(474)
Net income (loss) attributable to Loews Corporation	260	591	595
Eliminations [Member]
Revenues:
Intercompany interest and dividends	(816)	(782)	(736)
Total	(816)	(782)	(736)
Expenses:
Income (loss) before income tax	(816)	(782)	(736)
Income from continuing operations		(782)	(736)
Net income	(816)	(782)	(736)
Net income (loss) attributable to Loews Corporation	(816)	(782)	(736)
CNA Financial [Member]
Expenses:
Interest	155	183	166
Income (loss) before income tax	553	1,215	1,283
Income tax (expense) benefit	(71)	(322)	(363)
CNA Financial [Member] | Operating Segments [Member]
Revenues:
Insurance premiums	6,921	7,212	7,271
Net investment income	1,840	2,067	2,282
Investment gains (losses)	(71)	54	16
Other revenues	411	359	363
Total	9,101	9,692	9,932
Expenses:
Insurance claims and policyholders' benefits	5,384	5,591	5,806
Amortization of deferred acquisition costs	1,540	1,317	1,362
Other operating expenses	1,469	1,386	1,315
Interest	155	183	166
Total	8,548	8,477	8,649
Income (loss) before income tax	553	1,215	1,283
Income tax (expense) benefit	(71)	(322)	(363)
Income from continuing operations		893	920
Discontinued operations, net		(197)	22
Net income	482	696	942
Amounts attributable to noncontrolling interests	(49)	(71)	(95)
Net income (loss) attributable to Loews Corporation	433	625	847
Diamond Offshore [Member]
Expenses:
Interest	94	62	25
Income (loss) before income tax	(402)	514	774
Income tax (expense) benefit	117	(142)	(245)
Diamond Offshore [Member] | Operating Segments [Member]
Revenues:
Net investment income	3	1	1
Contract drilling revenues	2,360	2,737	2,844
Other revenues	65	87	81
Total	2,428	2,825	2,926
Expenses:
Contract drilling expenses	1,228	1,524	1,573
Other operating expenses	1,508	725	554
Interest	94	62	25
Total	2,830	2,311	2,152
Income (loss) before income tax	(402)	514	774
Income tax (expense) benefit	117	(142)	(245)
Income from continuing operations		372	529
Net income	(285)	372	529
Amounts attributable to noncontrolling interests	129	(189)	(272)
Net income (loss) attributable to Loews Corporation	(156)	183	257
Boardwalk Pipeline [Member]
Expenses:
Interest	176	165	163
Income (loss) before income tax	227	140	241
Income tax (expense) benefit	(46)	(11)	(56)
Boardwalk Pipeline [Member] | Operating Segments [Member]
Revenues:
Net investment income	1	1	1
Other revenues	1,253	1,235	1,231
Total	1,254	1,236	1,232
Expenses:
Other operating expenses	851	931	828
Interest	176	165	163
Total	1,027	1,096	991
Income (loss) before income tax	227	140	241
Income tax (expense) benefit	(46)	(11)	(56)
Income from continuing operations		129	185
Net income	181	129	185
Amounts attributable to noncontrolling interests	(107)	(111)	(107)
Net income (loss) attributable to Loews Corporation	74	18	78
Loews Hotels [Member]
Expenses:
Interest	21	14	9
Income (loss) before income tax	28	21	(4)
Income tax (expense) benefit	(16)	(10)	1
Loews Hotels [Member] | Operating Segments [Member]
Revenues:
Other revenues	604	475	380
Total	604	475	380
Expenses:
Other operating expenses	555	440	375
Interest	21	14	9
Total	576	454	384
Income (loss) before income tax	28	21	(4)
Income tax (expense) benefit	(16)	(10)	1
Income from continuing operations		11	(3)
Net income	12	11	(3)
Net income (loss) attributable to Loews Corporation	12	11	(3)
Corporate and Other [Member]
Revenues:
Net investment income	22	94	141
Intercompany interest and dividends	816	782	736
Other revenues	6	3	2
Total	844	879	879
Expenses:
Other operating expenses	116	103	98
Interest	74	74	62
Total	190	177	160
Income (loss) before income tax	654	702	719
Income tax (expense) benefit	59	28	7
Income from continuing operations		730	726
Discontinued operations, net		(194)	(574)
Net income	713	536	152
Net income (loss) attributable to Loews Corporation	$ 713	$ 536	$ 152