Consolidating Financial Information - Consolidating Statement of Income Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues:
Insurance premiums	$ 1,730	$ 1,735	$ 3,429	$ 3,422
Net investment income	587	510	1,009	1,098
Investment gains (losses)	1	(2)	(27)	8
Contract drilling revenues	357	617	801	1,217
Other revenues	632	575	1,268	1,168
Total			6,480	6,913
Expenses:
Insurance claims and policyholders' benefits	1,339	1,469	2,747	2,808
Amortization of deferred acquisition costs	305	314	612	617
Contract drilling expenses	198	344	411	695
Other operating expenses	1,611	879	2,518	2,128
Interest	130	134	273	265
Total	3,583	3,140	6,561	6,513
Income (loss) before income tax	(276)	295	(81)	400
Income tax (expense) benefit	(12)	(48)	(8)	(104)
Net income (loss)	(288)	247	(89)	296
Amounts attributable to noncontrolling interests	223	(77)	126	(17)
Net income (loss) attributable to Loews Corporation			37	279
Eliminations [Member]
Revenues:
Intercompany interest and dividends			(632)	(650)
Total			(632)	(650)
Expenses:
Income (loss) before income tax			(632)	(650)
Net income (loss)			(632)	(650)
Net income (loss) attributable to Loews Corporation			(632)	(650)
CNA Financial [Member]
Expenses:
Income (loss) before income tax	290	165	348	479
CNA Financial [Member] | Operating Segments [Member]
Revenues:
Insurance premiums			3,429	3,422
Net investment income			937	1,058
Investment gains (losses)			(15)	8
Other revenues			200	191
Total			4,551	4,679
Expenses:
Insurance claims and policyholders' benefits			2,747	2,808
Amortization of deferred acquisition costs			612	617
Other operating expenses			756	697
Interest			88	78
Total			4,203	4,200
Income (loss) before income tax			348	479
Income tax (expense) benefit			(71)	(107)
Net income (loss)			277	372
Amounts attributable to noncontrolling interests			(28)	(38)
Net income (loss) attributable to Loews Corporation			249	334
Diamond Offshore [Member]
Expenses:
Income (loss) before income tax	(657)	106	(574)	(181)
Diamond Offshore [Member] | Operating Segments [Member]
Revenues:
Net investment income				1
Investment gains (losses)			(12)
Contract drilling revenues			801	1,217
Other revenues			60	41
Total			849	1,259
Expenses:
Contract drilling expenses			411	695
Other operating expenses			974	696
Interest			50	49
Total			1,435	1,440
Income (loss) before income tax			(586)	(181)
Income tax (expense) benefit			100	22
Net income (loss)			(486)	(159)
Amounts attributable to noncontrolling interests			235	78
Net income (loss) attributable to Loews Corporation			(251)	(81)
Boardwalk Pipeline [Member]
Expenses:
Income (loss) before income tax	65	38	164	115
Boardwalk Pipeline [Member] | Operating Segments [Member]
Revenues:
Other revenues			655	629
Total			655	629
Expenses:
Other operating expenses			403	423
Interest			88	91
Total			491	514
Income (loss) before income tax			164	115
Income tax (expense) benefit			(35)	(21)
Net income (loss)			129	94
Amounts attributable to noncontrolling interests			(81)	(57)
Net income (loss) attributable to Loews Corporation			48	37
Loews Hotels [Member]
Expenses:
Income (loss) before income tax	$ 4	$ 14	13	24
Loews Hotels [Member] | Operating Segments [Member]
Revenues:
Other revenues			352	306
Total			352	306
Expenses:
Other operating expenses			328	272
Interest			11	10
Total			339	282
Income (loss) before income tax			13	24
Income tax (expense) benefit			(9)	(11)
Net income (loss)			4	13
Net income (loss) attributable to Loews Corporation			4	13
Corporate and Other [Member]
Revenues:
Net investment income			72	39
Intercompany interest and dividends			632	650
Other revenues			1	1
Total			705	690
Expenses:
Other operating expenses			57	40
Interest			36	37
Total			93	77
Income (loss) before income tax			612	613
Income tax (expense) benefit			7	13
Net income (loss)			619	626
Net income (loss) attributable to Loews Corporation			$ 619	$ 626