Segments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) Hotel subsidiary Segment mi	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Segments:
Number of reportable segments | Segment	4
Number of individual operating subsidiaries | subsidiary	3
Number of miles of natural gas and natural gas liquid pipelines | mi	14,315
Number of hotels | Hotel	25
Revenues:
Insurance premiums	$ 10,211	$ 9,480	$ 8,667
Net investment income (loss)	2,780	2,395	1,802
Investment gains (losses)	(81)	(53)	(199)
Non-insurance warranty revenue	1,609	1,624	1,574
Operating revenues and other	2,991	2,455	2,200
Total	17,510	15,901	14,044
Expenses:
Insurance claims and policyholders’ benefits	7,738	7,068	6,653
Amortization of deferred acquisition costs	1,798	1,644	1,490
Non-insurance warranty expense	1,547	1,544	1,471
Operating expenses and other	4,170	3,393	3,077
Equity method (income) loss	(58)	(120)	(139)
Interest	441	376	378
Total	15,636	13,905	12,930
Income (loss) before income tax	1,874	1,996	1,114
Income tax expense	(380)	(451)	(223)
Net income (loss)	1,494	1,545	891
Amounts attributable to noncontrolling interests	(80)	(111)	(69)
Net income (loss) attributable to Loews Corporation	1,414	1,434	822
Assets:
Assets	81,943	79,197
Pre-tax pension settlement charge	367
Unrecognized losses included in AOCI		47
Operating Expenses and Other:
Insurance related administrative expenses	1,275	1,251	1,160
Operating expenses and other	1,213	880	688
Depreciation and amortization	524	482	462
Other	1,158	780	767
Operating expenses and other	4,170	3,393	3,077
Property and casualty
Revenues:
Insurance premiums	9,774	9,029	8,194
Assets:
Loss from catastrophes		236	247
Total pretax (favorable) unfavorable development	48	48	(32)
CNA Financial
Revenues:
Insurance premiums	10,211	9,480	8,667
Net investment income (loss)	2,497	2,264	1,805
Investment gains (losses)	(81)	(99)	(199)
Non-insurance warranty revenue	1,609	1,624	1,574
Operating revenues and other	34	30	32
Total	14,270	13,299	11,879
Expenses:
Insurance claims and policyholders’ benefits	7,738	7,068	6,653
Amortization of deferred acquisition costs	1,798	1,644	1,490
Non-insurance warranty expense	1,547	1,544	1,471
Operating expenses and other	1,843	1,398	1,339
Equity method (income) loss
Interest	133	127	112
Total	13,059	11,781	11,065
Income (loss) before income tax	1,211	1,518	814
Income tax expense	(252)	(313)	(133)
Net income (loss)	959	1,205	681
Amounts attributable to noncontrolling interests	(80)	(111)	(69)
Net income (loss) attributable to Loews Corporation	879	1,094	612
Assets:
Assets	66,434	64,655
Operating Expenses and Other:
Insurance related administrative expenses	1,275	1,251	1,160
Operating expenses and other
Depreciation and amortization
Other	568	147	179
Operating expenses and other	1,843	1,398	1,339
CNA Financial | Property and casualty
Assets:
Loss from catastrophes	358
Total pretax (favorable) unfavorable development	48
Boardwalk Pipelines
Revenues:
Insurance premiums
Net investment income (loss)	32	11	3
Investment gains (losses)
Non-insurance warranty revenue
Operating revenues and other	2,033	1,625	1,443
Total	2,065	1,636	1,446
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	1,377	1,108	950
Equity method (income) loss
Interest	183	155	166
Total	1,560	1,263	1,116
Income (loss) before income tax	505	373	330
Income tax expense	(92)	(90)	(83)
Net income (loss)	413	283	247
Amounts attributable to noncontrolling interests
Net income (loss) attributable to Loews Corporation	413	283	247
Assets:
Assets	9,853	9,785
Operating Expenses and Other:
Insurance related administrative expenses
Operating expenses and other	633	395	274
Depreciation and amortization	429	412	396
Other	315	301	280
Operating expenses and other	1,377	1,108	950
Lodging and related services – Loews Hotels & Co
Revenues:
Insurance premiums
Net investment income (loss)	9	6	1
Investment gains (losses)		46
Non-insurance warranty revenue
Operating revenues and other	924	800	720
Total	933	852	721
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	873	767	697
Equity method (income) loss	(86)	(129)	(148)
Interest	51	14	11
Total	838	652	560
Income (loss) before income tax	95	200	161
Income tax expense	(25)	(53)	(44)
Net income (loss)	70	147	117
Amounts attributable to noncontrolling interests
Net income (loss) attributable to Loews Corporation	70	147	117
Assets:
Assets	2,498	2,374
Operating Expenses and Other:
Insurance related administrative expenses
Operating expenses and other	580	485	414
Depreciation and amortization	93	69	64
Other	200	213	219
Operating expenses and other	$ 873	767	697
Lodging and related services – Loews Hotels & Co | Lodging and related services – Loews Hotels & Co
Segments:
Number of hotels | Hotel	11
Lodging and related services – Loews Hotels & Co | Joint Ventures
Segments:
Number of hotels | Hotel	12
Lodging and related services – Loews Hotels & Co | Unaffiliated Owners
Segments:
Number of hotels | Hotel	2
Corporate
Revenues:
Insurance premiums
Net investment income (loss)	242	114	(7)
Investment gains (losses)
Non-insurance warranty revenue
Operating revenues and other			5
Total	242	114	(2)
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	77	120	91
Equity method (income) loss	28	9	9
Interest	74	80	89
Total	179	209	189
Income (loss) before income tax	63	(95)	(191)
Income tax expense	(11)	5	37
Net income (loss)	52	(90)	(154)
Amounts attributable to noncontrolling interests
Net income (loss) attributable to Loews Corporation	52	(90)	(154)
Assets:
Assets	3,158	2,383
Operating Expenses and Other:
Insurance related administrative expenses
Operating expenses and other
Depreciation and amortization	2	1	2
Other	75	119	89
Operating expenses and other	$ 77	$ 120	$ 91
United States | Lodging and related services – Loews Hotels & Co
Segments:
Number of hotels | Hotel	24
Canada | Lodging and related services – Loews Hotels & Co
Segments:
Number of hotels | Hotel	1