Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers	$ 697	$ 959
Other revenues	18	23
Operating revenues and other	715	982
Deferred Revenue [Abstract]
Deferred revenue	4,119		$ 4,023
Revenue recognized	316	297
Performance Obligations [Abstract]
Remaining performance obligations	13,300
Receivables [Member]
Receivables from Contracts with Customers [Abstract]
Receivables from contracts with customers	251		246
Other Liabilities [Member]
Deferred Revenue [Abstract]
Deferred revenue	4,200		$ 4,100
CNA Financial [Member] | Non-Insurance Warranty [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers	338	301
Boardwalk Pipelines [Member] | Transportation and Storage of Natural Gas and NGLs and Other Services [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers	361	332
Loews Hotels & Co [Member] | Lodging and Related Services [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers	56	142
Corporate [Member] | Rigid Plastic Packaging and Recycled Resin [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers	280	256
Diamond Offshore [Member] | Contract Drilling [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		$ 229
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01
Performance Obligations [Abstract]
Remaining performance obligations	$ 1,900
Expected timing of satisfaction	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Performance Obligations [Abstract]
Remaining performance obligations	$ 2,100
Expected timing of satisfaction	1 year