Segments (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) subsidiary segment	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Segments:
Number of reportable segments | segment			4
Number of individual operating subsidiaries | subsidiary			3
Revenues:
Insurance premiums	$ 2,783	$ 2,593	$ 8,103	$ 7,532
Net investment income	743	776	2,065	2,084
Investment losses	(7)	(10)	(62)	(42)
Non-insurance warranty revenue	393	401	1,188	1,212
Operating revenues and other	759	706	2,426	2,178
Total	4,671	4,466	13,720	12,964
Expenses:
Insurance claims and policyholders’ benefits	2,032	2,019	6,144	5,708
Amortization of deferred acquisition costs	483	457	1,423	1,336
Non-insurance warranty expense	377	387	1,146	1,169
Operating expenses and other	1,000	930	2,980	2,778
Equity method (income) loss	(22)	9	(39)	(44)
Interest	112	114	324	331
Total	3,982	3,916	11,978	11,278
Income before income tax	689	550	1,742	1,686
Income tax (expense) benefit	(153)	(125)	(398)	(381)
Net income	536	425	1,344	1,305
Amounts attributable to noncontrolling interests	(32)	(24)	(79)	(78)
Net income attributable to Loews Corporation	504	401	1,265	1,227
Assets:
Assets	85,941	83,617	85,941	83,617	$ 81,943
Operating Expenses and Other:
Insurance related administrative expenses	324	321	982	937
Operating expenses	334	292	1,003	865
Depreciation and amortization	135	132	410	392
Other	207	185	585	584
Operating expenses and other	1,000	930	2,980	2,778
Total pretax (favorable) unfavorable development
Assets:
Total pretax (favorable) unfavorable development	(1)	17	190	33
Operating Segments | CNA Financial
Revenues:
Insurance premiums	2,783	2,593	8,103	7,532
Net investment income	638	626	1,904	1,853
Investment losses	(7)	(10)	(62)	(42)
Non-insurance warranty revenue	393	401	1,188	1,212
Operating revenues and other	10	8	28	26
Total	3,817	3,618	11,161	10,581
Expenses:
Insurance claims and policyholders’ benefits	2,032	2,019	6,144	5,708
Amortization of deferred acquisition costs	483	457	1,423	1,336
Non-insurance warranty expense	377	387	1,146	1,169
Operating expenses and other	376	362	1,107	1,077
Equity method (income) loss
Interest	36	32	99	101
Total	3,304	3,257	9,919	9,391
Income before income tax	513	361	1,242	1,190
Income tax (expense) benefit	(110)	(78)	(266)	(252)
Net income	403	283	976	938
Amounts attributable to noncontrolling interests	(32)	(24)	(79)	(78)
Net income attributable to Loews Corporation	371	259	897	860
Assets:
Assets	69,704	67,305	69,704	67,305
Operating Expenses and Other:
Insurance related administrative expenses	324	321	982	937
Operating expenses
Depreciation and amortization
Other	52	41	125	140
Operating expenses and other	376	362	1,107	1,077
Operating Segments | CNA Financial | Total pretax (favorable) unfavorable development
Assets:
Loss from catastrophes	41	143	200	313
Total pretax (favorable) unfavorable development	(1)	17	190	33
Operating Segments | Boardwalk Pipelines
Revenues:
Insurance premiums
Net investment income	4	9	8	22
Investment losses
Non-insurance warranty revenue
Operating revenues and other	542	474	1,697	1,466
Total	546	483	1,705	1,488
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	382	332	1,143	991
Equity method (income) loss
Interest	40	47	119	137
Total	422	379	1,262	1,128
Income before income tax	124	104	443	360
Income tax (expense) benefit	(30)	(27)	(109)	(92)
Net income	94	77	334	268
Amounts attributable to noncontrolling interests
Net income attributable to Loews Corporation	94	77	334	268
Assets:
Assets	10,133	10,535	10,133	10,535
Operating Expenses and Other:
Insurance related administrative expenses
Operating expenses	190	147	559	434
Depreciation and amortization	107	107	333	321
Other	85	78	251	236
Operating expenses and other	382	332	1,143	991
Operating Segments | Loews Hotels & Co
Revenues:
Insurance premiums
Net investment income	4	2	9	7
Investment losses
Non-insurance warranty revenue
Operating revenues and other	207	224	701	686
Total	211	226	710	693
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	221	218	678	652
Equity method (income) loss	(25)		(60)	(59)
Interest	18	17	52	37
Total	214	235	670	630
Income before income tax	(3)	(9)	40	63
Income tax (expense) benefit		1	(15)	(20)
Net income	(3)	(8)	25	43
Amounts attributable to noncontrolling interests
Net income attributable to Loews Corporation	(3)	(8)	25	43
Assets:
Assets	2,502	2,497	2,502	2,497
Operating Expenses and Other:
Insurance related administrative expenses
Operating expenses	144	145	444	431
Depreciation and amortization	27	24	75	69
Other	50	49	159	152
Operating expenses and other	221	218	678	652
Segment Reconciling Items | Corporate
Revenues:
Insurance premiums
Net investment income	97	139	144	202
Investment losses
Non-insurance warranty revenue
Operating revenues and other
Total	97	139	144	202
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	21	18	52	58
Equity method (income) loss	3	9	21	15
Interest	18	18	54	56
Total	42	45	127	129
Income before income tax	55	94	17	73
Income tax (expense) benefit	(13)	(21)	(8)	(17)
Net income	42	73	9	56
Amounts attributable to noncontrolling interests
Net income attributable to Loews Corporation	42	73	9	56
Assets:
Assets	3,602	3,280	3,602	3,280
Operating Expenses and Other:
Insurance related administrative expenses
Operating expenses
Depreciation and amortization	1	1	2	2
Other	20	17	50	56
Operating expenses and other	$ 21	$ 18	$ 52	$ 58