Revenue from Contracts with Customers (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		$ 2,820	$ 3,870	$ 3,886
Other revenues		113	68	101
Operating revenues and other		2,933	3,938	3,987
Deferred Revenue [Abstract]
Deferred revenue		4,023	3,779
Revenue recognized		1,100	1,000
Contract Costs [Abstract]
Contract costs		3,068	2,840
Amortization of contract costs		907	912
Adjustments to deferred costs		0	0
Performance Obligations [Abstract]
Remaining performance obligations		13,400
Receivables [Member]
Receivables from Contracts with Customers [Abstract]
Receivables from contracts with customers		246	458
Other Liabilities [Member]
Deferred Revenue [Abstract]
Deferred revenue		4,100	3,900
Deferred Non-insurance Warranty Acquisition Expenses [Member]
Contract Costs [Abstract]
Contract costs		3,100	2,900
CNA Financial [Member] | Non-Insurance Warranty [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		1,252	1,161	1,007
Boardwalk Pipelines [Member] | Transportation and Storage of Natural Gas and NGLs and Other Services [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		1,264	1,266	1,206
Loews Hotels & Co [Member] | Lodging and Related Services [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		234	691	730
Corporate [Member] | Rigid Plastic Packaging and Recycled Resin [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers		1,022	932	867
Diamond Offshore [Member] | Contract Drilling [Member]
Disaggregation of Revenues [Abstract]
Revenues from contracts with customers	[1]	300	$ 981	$ 1,083
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Performance Obligations [Abstract]
Remaining performance obligations		$ 2,400
Expected timing of satisfaction		1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Performance Obligations [Abstract]
Remaining performance obligations		$ 2,000
Expected timing of satisfaction		1 year

[1] Revenues presented for Diamond Offshore reflect the periods prior to deconsolidation. See Notes 2 and 20 for further discussion