Supplemental Quarterly Information (Unaudited) - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income (loss) attributable to Loews Corporation	$ 355	$ (22)	$ 167	$ 322	$ 1,434	$ 822	$ 1,562
Effect of changes in discount rate	125				578	125	5,942	$ 7,395
Gross premium		125			$ 451	473	491
Effect of Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income (loss) attributable to Loews Corporation	$ (9)	$ (152)	$ (13)	$ (16)		$ (190)	$ (16)