Debt - Schedule of Debt by Subsidiary (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Principal	$ 11,643	$ 11,488
Unamortized Discount and Issuance Costs	110	112
Net	11,533	11,376
Short Term Debt	77	17
Long term debt	11,456	11,359
Loews Corporation [Member]
Debt Instrument [Line Items]
Principal	1,800
Unamortized Discount and Issuance Costs	21
Net	1,779
Long term debt	1,779
CNA Financial [Member]
Debt Instrument [Line Items]
Principal	2,693
Unamortized Discount and Issuance Costs	14
Net	2,679
Long term debt	2,679
Diamond Offshore [Member]
Debt Instrument [Line Items]
Principal	2,000
Unamortized Discount and Issuance Costs	24
Net	1,976
Long term debt	1,976
Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Principal	3,592
Unamortized Discount and Issuance Costs	26
Net	3,566
Long term debt	3,566
Loews Hotels And Co [Member]
Debt Instrument [Line Items]
Principal	712	$ 653
Unamortized Discount and Issuance Costs	7
Net	705
Short Term Debt	67
Long term debt	638
Altium Packaging [Member]
Debt Instrument [Line Items]
Principal	846
Unamortized Discount and Issuance Costs	18
Net	828
Short Term Debt	10
Long term debt	$ 818

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount of long-term debt and lease obligation, classified as noncurrent.

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