Revenue from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		$ 425	$ 569	$ 1,518	$ 2,145
Other revenues		25	40	62	96
Operating revenues and other		450	609	1,580	2,241
Deferred Revenue [Abstract]
Deferred revenue		4,443		4,443		$ 4,023
Revenue recognized				916	839
Performance Obligations [Abstract]
Remaining performance obligations		13,300		13,300
Receivables [Member]
Receivables from Contracts with Customers [Abstract]
Receivables from contracts with customers		118		118		246
Other Liabilities [Member]
Deferred Revenue [Abstract]
Deferred revenue		4,500		4,500		$ 4,100
CNA Financial [Member] | Non-Insurance Warranty [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		357	317	1,054	926
Boardwalk Pipelines [Member] | Transportation and Storage of Natural Gas and NGLs and Other Services [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		296	280	959	898
Loews Hotels & Co [Member] | Lodging and Related Services [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		129	36	279	194
Corporate [Member] | Rigid Plastic Packaging and Recycled Resin [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers	[1]		$ 253	280	753
Diamond Offshore [Member] | Contract Drilling [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers	[2]				$ 300
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Performance Obligations [Abstract]
Remaining performance obligations		$ 700		$ 700
Expected timing of satisfaction		3 months		3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Performance Obligations [Abstract]
Remaining performance obligations		$ 2,300		$ 2,300
Expected timing of satisfaction		1 year		1 year

[1] Revenues presented for Corporate reflect the periods prior to the deconsolidation of Altium Packaging in the second quarter of 2021. See Note 2 for further discussion.

[2] Revenues presented for Diamond Offshore reflect the period prior to its deconsolidation in the second quarter of 2020. See Note 2 for further discussion.