Supplemental Quarterly Information (Unaudited) - Effect of adoption of ASU 2018-12 (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
Net income (loss) attributable to Loews Corporation
Net income (loss) attributable to Loews Corporation	$ 355	$ (22)	$ 167	$ 322	$ 1,434	$ 822	$ 1,562
Other comprehensive income (loss)
Other comprehensive income (loss)	$ 400	$ (839)	$ (778)	$ (1,002)	$ 961	$ (2,219)	$ 215
Diluted Net Income (Loss) Per Share
Net income (loss) attributable to Loews Corporation (in dollars per share)	$ 1.49	$ (0.09)	$ 0.68	$ 1.29	$ 6.29	$ 3.38	$ 6.00
As Reported
Net income (loss) attributable to Loews Corporation
Net income (loss) attributable to Loews Corporation	$ 364	$ 130	$ 180	$ 338		$ 1,012	$ 1,578
Other comprehensive income (loss)
Other comprehensive income (loss)	$ 577	$ (1,425)	$ (1,405)	$ (1,605)		$ (3,858)	$ (445)
Diluted Net Income (Loss) Per Share
Net income (loss) attributable to Loews Corporation (in dollars per share)	$ 1.53	$ 0.54	$ 0.73	$ 1.36		$ 4.16	$ 6.07
Effect of Adoption
Net income (loss) attributable to Loews Corporation
Net income (loss) attributable to Loews Corporation	$ (9)	$ (152)	$ (13)	$ (16)		$ (190)	$ (16)
Other comprehensive income (loss)
Other comprehensive income (loss)	$ (177)	$ 586	$ 627	$ 603		$ 1,639	$ 660
Diluted Net Income (Loss) Per Share
Net income (loss) attributable to Loews Corporation (in dollars per share)	$ (0.04)	$ (0.63)	$ (0.05)	$ (0.07)		$ (0.78)	$ (0.07)