Debt - Schedule of Debt (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt [Abstract]
Total long term debt and finance lease obligation	$ 9,063,000,000	$ 9,080,000,000
Less unamortized discount and issuance costs	60,000,000	61,000,000
Debt, net	9,003,000,000	9,019,000,000
Loews Corporation
Debt [Abstract]
Total long term debt and finance lease obligation	1,800,000,000
Less unamortized discount and issuance costs	18,000,000
Debt, net	1,782,000,000
Loews Corporation | 2.6% Senior Notes Due 2023
Debt [Abstract]
Long term debt		500,000,000
Interest rate	2.60%
Maturity year	2023
Effective interest rate	2.80%
Debt authorized	$ 500,000,000
Loews Corporation | 3.8% Senior Notes Due 2026
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	3.80%
Maturity year	2026
Effective interest rate	3.90%
Debt authorized	$ 500,000,000
Loews Corporation | 3.2% Senior Notes Due 2030
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	3.20%
Maturity year	2030
Effective interest rate	3.30%
Debt authorized	$ 500,000,000
Loews Corporation | 6.0% Senior Notes Due 2035
Debt [Abstract]
Long term debt	$ 300,000,000	300,000,000
Interest rate	6.00%
Maturity year	2035
Effective interest rate	6.20%
Debt authorized	$ 300,000,000
Loews Corporation | 4.1% Senior Notes Due 2043
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	4.10%
Maturity year	2043
Effective interest rate	4.30%
Debt authorized	$ 500,000,000
CNA Financial
Debt [Abstract]
Total long term debt and finance lease obligation	3,050,000,000
Less unamortized discount and issuance costs	19,000,000
Debt, net	3,031,000,000
CNA Financial | 7.3% Senior Debentures Due 2023
Debt [Abstract]
Long term debt		243,000,000
Interest rate	7.30%
Maturity year	2023
Effective interest rate	7.30%
Debt authorized	$ 250,000,000
CNA Financial | 4.0% Senior Notes Due 2024
Debt [Abstract]
Long term debt	$ 550,000,000	550,000,000
Interest rate	4.00%
Maturity year	2024
Effective interest rate	4.00%
Debt authorized	$ 550,000,000
CNA Financial | 4.5% Senior Notes Due 2026
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	4.50%
Maturity year	2026
Effective interest rate	4.50%
Debt authorized	$ 500,000,000
CNA Financial | 3.5% Senior Notes Due 2027
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	3.50%
Maturity year	2027
Effective interest rate	3.50%
Debt authorized	$ 500,000,000
CNA Financial | 3.9% Senior Notes Due 2029
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	3.90%
Maturity year	2029
Effective interest rate	3.90%
Debt authorized	$ 500,000,000
CNA Financial | 2.1% Senior Notes Due 2030
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	2.10%
Maturity year	2030
Effective interest rate	2.10%
Debt authorized	$ 500,000,000
CNA Financial | 5.5% Senior Notes Due 2033
Debt [Abstract]
Long term debt	$ 500,000,000
Interest rate	5.50%
Maturity year	2033
Effective interest rate	5.70%
Debt authorized	$ 500,000,000
Boardwalk Pipelines
Debt [Abstract]
Finance lease obligation	5,000,000	5,000,000
Total long term debt and finance lease obligation	3,280,000,000
Less unamortized discount and issuance costs	17,000,000
Debt, net	3,263,000,000
Boardwalk Pipelines | Variable rate revolving credit facility due 2028
Debt [Abstract]
Long term debt	$ 25,000,000
Maturity year	2028
Effective interest rate	6.70%
Boardwalk Pipelines | 5.0% Senior Notes Due 2024
Debt [Abstract]
Long term debt	$ 600,000,000	600,000,000
Interest rate	5.00%
Maturity year	2024
Effective interest rate	5.20%
Debt authorized	$ 600,000,000
Boardwalk Pipelines | 6.0% Senior Notes Due 2026
Debt [Abstract]
Long term debt	$ 550,000,000	550,000,000
Interest rate	6.00%
Maturity year	2026
Effective interest rate	6.20%
Debt authorized	$ 550,000,000
Boardwalk Pipelines | 4.5% Senior Notes Due 2027
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	4.50%
Maturity year	2027
Effective interest rate	4.60%
Debt authorized	$ 500,000,000
Boardwalk Pipelines | 7.3% Senior Debentures Due 2027
Debt [Abstract]
Long term debt	$ 100,000,000	100,000,000
Interest rate	7.30%
Maturity year	2027
Effective interest rate	8.10%
Debt authorized	$ 100,000,000
Boardwalk Pipelines | 4.8% Senior Notes Due 2029
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	4.80%
Maturity year	2029
Effective interest rate	4.90%
Debt authorized	$ 500,000,000
Boardwalk Pipelines | 3.4% Senior Notes Due 2031
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	3.40%
Maturity year	2031
Effective interest rate	3.50%
Debt authorized	$ 500,000,000
Boardwalk Pipelines | 3.6% Senior Notes Due 2032
Debt [Abstract]
Long term debt	$ 500,000,000	500,000,000
Interest rate	3.60%
Maturity year	2032
Effective interest rate	3.70%
Debt authorized	$ 500,000,000
Loews Hotels & Co
Debt [Abstract]
Total long term debt and finance lease obligation	933,000,000
Less unamortized discount and issuance costs	6,000,000
Debt, net	927,000,000
Loews Hotels & Co | Senior Debt, Principally Mortgages
Debt [Abstract]
Long term debt	$ 933,000,000	$ 732,000,000
Effective interest rate	6.80%	5.50%