Summary of Significant Accounting Policies - Adoption on Consolidated Condensed Statement of Comprehensive Income (Loss) (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
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Changes in: Net unrealized losses on other investments					$ 1,125	$ (6,097)	$ (987)
Total unrealized losses on investments					1,120	(6,102)	(989)
Impact of changes in discount rates used to measure long-duration contract liabilities					(318)	3,959	941
Other comprehensive income (loss)	$ 400	$ (839)	$ (778)	$ (1,002)	961	(2,219)	215
Comprehensive income (loss)					2,506	(1,328)	1,900
Amounts attributable to noncontrolling interests					(188)	150	(142)
Total comprehensive income (loss) attributable to Loews Corporation					$ 2,318	(1,178)	1,758
As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Changes in: Net unrealized losses on other investments						(3,777)	(706)
Total unrealized losses on investments						(3,782)	(708)
Other comprehensive income (loss)	577	(1,425)	(1,405)	(1,605)		(3,858)	(445)
Comprehensive income (loss)						(2,755)	1,258
Amounts attributable to noncontrolling interests						297	(75)
Total comprehensive income (loss) attributable to Loews Corporation						(2,458)	1,183
Effect of Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Changes in: Net unrealized losses on other investments						(2,320)	(281)
Total unrealized losses on investments						(2,320)	(281)
Impact of changes in discount rates used to measure long-duration contract liabilities						3,959	941
Other comprehensive income (loss)	$ (177)	$ 586	$ 627	$ 603		1,639	660
Comprehensive income (loss)						1,427	642
Amounts attributable to noncontrolling interests						(147)	(67)
Total comprehensive income (loss) attributable to Loews Corporation						$ 1,280	$ 575