Segments (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) Segment subsidiary	Jun. 30, 2022 USD ($)
Segments [Abstract]
Number of reportable segments | Segment			4
Number of individual operating subsidiaries | subsidiary			3
Revenues:
Insurance premiums	$ 2,347	$ 2,155	$ 4,595	$ 4,214
Net investment income	592	366	1,161	798
Investment gains (losses)	14	(59)	(21)	(70)
Non-insurance warranty revenue	407	392	814	774
Operating revenues and other	574	534	1,168	1,074
Total	3,934	3,388	7,717	6,790
Expenses:
Insurance claims and policyholders’ benefits	1,779	1,601	3,432	3,079
Amortization of deferred acquisition costs	403	374	782	718
Non-insurance warranty expense	384	367	768	721
Operating expenses and other	808	766	1,589	1,482
Equity method (income) loss	(39)	(51)	(67)	(76)
Interest	91	96	186	192
Total	3,426	3,153	6,690	6,116
Income (loss) before income tax	508	235	1,027	674
Income tax (expense) benefit	(120)	(48)	(235)	(135)
Net income	388	187	792	539
Amounts attributable to noncontrolling interests	(28)	(20)	(57)	(50)
Net income attributable to Loews Corporation	360	167	735	489
CNA Financial
Expenses:
Insurance claims and policyholders’ benefits		1,601		3,079
Income tax (expense) benefit		(37)		(97)
Net income		190		485
Amounts attributable to noncontrolling interests		(20)		(50)
Net income attributable to Loews Corporation		170		435
Operating Segments | CNA Financial
Revenues:
Insurance premiums	2,347	2,155	4,595	4,214
Net investment income	575	432	1,100	880
Investment gains (losses)	(32)	(59)	(67)	(70)
Non-insurance warranty revenue	407	392	814	774
Operating revenues and other	7	6	14	13
Total	3,304	2,926	6,456	5,811
Expenses:
Insurance claims and policyholders’ benefits	1,779	1,601	3,432	3,079
Amortization of deferred acquisition costs	403	374	782	718
Non-insurance warranty expense	384	367	768	721
Operating expenses and other	346	329	683	655
Equity method (income) loss
Interest	31	28	59	56
Total	2,943	2,699	5,724	5,229
Income (loss) before income tax	361	227	732	582
Income tax (expense) benefit	(78)	(37)	(152)	(97)
Net income	283	190	580	485
Amounts attributable to noncontrolling interests	(28)	(20)	(57)	(50)
Net income attributable to Loews Corporation	255	170	523	435
Operating Segments | Boardwalk Pipelines
Revenues:
Insurance premiums
Net investment income	5		6
Investment gains (losses)
Non-insurance warranty revenue
Operating revenues and other	360	325	756	706
Total	365	325	762	706
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	250	231	492	448
Equity method (income) loss
Interest	39	42	78	84
Total	289	273	570	532
Income (loss) before income tax	76	52	192	174
Income tax (expense) benefit	(19)	(13)	(49)	(44)
Net income	57	39	143	130
Amounts attributable to noncontrolling interests
Net income attributable to Loews Corporation	57	39	143	130
Operating Segments | Loews Hotels & Co
Revenues:
Insurance premiums
Net investment income	1	(1)	2	(1)
Investment gains (losses)	46		46
Non-insurance warranty revenue
Operating revenues and other	207	201	398	353
Total	254	200	446	352
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	194	185	377	337
Equity method (income) loss	(41)	(53)	(72)	(79)
Interest		4	6	8
Total	153	136	311	266
Income (loss) before income tax	101	64	135	86
Income tax (expense) benefit	(27)	(20)	(37)	(27)
Net income	74	44	98	59
Amounts attributable to noncontrolling interests
Net income attributable to Loews Corporation	74	44	98	59
Corporate
Revenues:
Insurance premiums
Net investment income	11	(65)	53	(81)
Investment gains (losses)
Non-insurance warranty revenue
Operating revenues and other		2		2
Total	11	(63)	53	(79)
Expenses:
Insurance claims and policyholders’ benefits
Amortization of deferred acquisition costs
Non-insurance warranty expense
Operating expenses and other	18	21	37	42
Equity method (income) loss	2	2	5	3
Interest	21	22	43	44
Total	41	45	85	89
Income (loss) before income tax	(30)	(108)	(32)	(168)
Income tax (expense) benefit	4	22	3	33
Net income	(26)	(86)	(29)	(135)
Amounts attributable to noncontrolling interests
Net income attributable to Loews Corporation	$ (26)	$ (86)	$ (29)	$ (135)