Summary of Significant Accounting Policies - Effects of Adoption of ASU 2018-12, Operations (Details) - USD ($) $ / shares in Units, $ 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
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance claims and policyholders’ benefits					$ 7,068	$ 6,653	$ 6,371
Income before income tax					1,996	1,114	2,160
Income tax expense					(451)	(223)	(475)
Net income					1,545	891	1,685
Amounts attributable to noncontrolling interests					(111)	(69)	(123)
Net income attributable to Loews Corporation	$ 355	$ (22)	$ 167	$ 322	$ 1,434	$ 822	$ 1,562
Basic net income per share (in dollars per share)					$ 6.30	$ 3.39	$ 6.02
Diluted net income per share (in dollars per share)	$ 1.49	$ (0.09)	$ 0.68	$ 1.29	$ 6.29	$ 3.38	$ 6.00
Re-measurement loss of insurance claims and policyholders’ benefits					$ (88)	$ (214)	$ (8)
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance claims and policyholders’ benefits						6,386	6,349
Income before income tax						1,381	2,182
Income tax expense						(278)	(479)
Net income						1,103	1,703
Amounts attributable to noncontrolling interests						(91)	(125)
Net income attributable to Loews Corporation	$ 364	$ 130	$ 180	$ 338		$ 1,012	$ 1,578
Basic net income per share (in dollars per share)						$ 4.17	$ 6.08
Diluted net income per share (in dollars per share)	$ 1.53	$ 0.54	$ 0.73	$ 1.36		$ 4.16	$ 6.07
Effect of Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance claims and policyholders’ benefits						$ 267	$ 22
Income before income tax						(267)	(22)
Income tax expense						55	4
Net income						(212)	(18)
Amounts attributable to noncontrolling interests						22	2
Net income attributable to Loews Corporation	$ (9)	$ (152)	$ (13)	$ (16)		$ (190)	$ (16)
Basic net income per share (in dollars per share)						$ (0.78)	$ (0.06)
Diluted net income per share (in dollars per share)	$ (0.04)	$ (0.63)	$ (0.05)	$ (0.07)		$ (0.78)	$ (0.07)