Segments (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) subsidiary Segment	Sep. 30, 2022 USD ($)
Segments [Abstract]
Number of reportable segments | Segment			4
Number of individual operating subsidiaries | subsidiary			3
Revenues:
Insurance premiums	$ 2,406	$ 2,221	$ 7,001	$ 6,435
Net investment income	592	404	1,752	1,202
Investment gains (losses)	(38)	(96)	(59)	(166)
Non-insurance warranty revenue	407	399	1,221	1,173
Operating revenues and other	559	533	1,728	1,607
Total	3,926	3,461	11,643	10,251
Expenses:
Insurance claims and policyholders’ benefits	1,826	1,880	5,258	4,959
Amortization of deferred acquisition costs	426	383	1,208	1,101
Non-insurance warranty expense	386	371	1,154	1,092
Operating expenses and other	860	795	2,449	2,277
Equity method (income) loss	(22)	(35)	(89)	(111)
Interest	94	92	280	284
Total	3,570	3,486	10,260	9,602
Income (loss) before income tax	356	(25)	1,383	649
Income tax (expense) benefit	(80)	(2)	(315)	(137)
Net income (loss)	276	(27)	1,068	512
Amounts attributable to noncontrolling interests	(23)	5	(80)	(45)
Net income (loss) attributable to Loews Corporation	253	(22)	988	467
CNA Financial
Expenses:
Insurance claims and policyholders’ benefits		1,880		4,959
Income tax (expense) benefit		9		(88)
Net income (loss)		(42)		443
Amounts attributable to noncontrolling interests		5		(45)
Net income (loss) attributable to Loews Corporation		(37)		398
Operating Segments | CNA Financial
Revenues:
Insurance premiums	2,406	2,221	7,001	6,435
Net investment income	553	422	1,653	1,302
Investment gains (losses)	(38)	(96)	(105)	(166)
Non-insurance warranty revenue	407	399	1,221	1,173
Operating revenues and other	8	11	22	24
Total	3,336	2,957	9,792	8,768
Expenses:
Insurance claims and policyholders’ benefits	1,826	1,880	5,258	4,959
Amortization of deferred acquisition costs	426	383	1,208	1,101
Non-insurance warranty expense	386	371	1,154	1,092
Operating expenses and other	338	346	1,021	1,001
Equity method (income) loss
Interest	34	28	93	84
Total	3,010	3,008	8,734	8,237
Income (loss) before income tax	326	(51)	1,058	531
Income tax (expense) benefit	(68)	9	(220)	(88)
Net income (loss)	258	(42)	838	443
Amounts attributable to noncontrolling interests	(23)	5	(80)	(45)
Net income (loss) attributable to Loews Corporation	235	(37)	758	398
Operating Segments | Boardwalk Pipelines
Revenues:
Insurance premiums
Net investment income	6	1	11	1
Investment gains (losses)
Non-insurance warranty revenue
Operating revenues and other	357	338	1,114	1,044
Total	363	339	1,125	1,045
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	258	250	751	698
Equity method (income) loss
Interest	39	42	117	126
Total	297	292	868	824
Income (loss) before income tax	66	47	257	221
Income tax (expense) benefit	(17)	(13)	(66)	(57)
Net income (loss)	49	34	191	164
Amounts attributable to noncontrolling interests
Net income (loss) attributable to Loews Corporation	49	34	191	164
Operating Segments | Loews Hotels & Co
Revenues:
Insurance premiums
Net investment income	2		4	(1)
Investment gains (losses)			46
Non-insurance warranty revenue
Operating revenues and other	194	180	592	533
Total	196	180	642	532
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	195	183	572	520
Equity method (income) loss	(26)	(36)	(98)	(115)
Interest	3	(1)	9	7
Total	172	146	483	412
Income (loss) before income tax	24	34	159	120
Income tax (expense) benefit	(7)	(9)	(44)	(36)
Net income (loss)	17	25	115	84
Amounts attributable to noncontrolling interests
Net income (loss) attributable to Loews Corporation	17	25	115	84
Segment Reconciling Items | Corporate
Revenues:
Insurance premiums
Net investment income	31	(19)	84	(100)
Investment gains (losses)
Non-insurance warranty revenue
Operating revenues and other		4		6
Total	31	(15)	84	(94)
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	69	16	105	58
Equity method (income) loss	4	1	9	4
Interest	18	23	61	67
Total	91	40	175	129
Income (loss) before income tax	(60)	(55)	(91)	(223)
Income tax (expense) benefit	12	11	15	44
Net income (loss)	(48)	(44)	(76)	(179)
Amounts attributable to noncontrolling interests
Net income (loss) attributable to Loews Corporation	$ (48)	$ (44)	$ (76)	$ (179)