Schedule I - Condensed Financial Information of Registrant - Parent Company Only, Statements of Income and Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Equity in income of subsidiaries									$ 69	$ 73	$ 81
Total	$ 3,876	$ 3,675	$ 3,623	$ 3,757	$ 3,287	$ 3,608	$ 3,590	$ 3,581	14,931	14,066	13,735
Expenses:
Interest									591	574	646
Total									13,812	13,232	12,153
Income before income tax									1,119	834	1,582
Income tax (expense) benefit									248	128	170
Net income									871	706	1,412
Total comprehensive income (loss) attributable to Loews Corporation									1,744	(161)	1,361
Loews Corporation [Member]
Revenues:
Equity in income of subsidiaries									867	819	1,199
Net investment income (loss), interest and other									239	(11)	167
Total									1,106	808	1,366
Expenses:
Administrative									83	127	134
Interest									72	72	72
Total									155	199	206
Income before income tax									951	609	1,160
Income tax (expense) benefit									(19)	27	4
Net income									932	636	1,164
Equity in other comprehensive income (loss) of subsidiaries									812	(797)	197
Total comprehensive income (loss) attributable to Loews Corporation									$ 1,744	$ (161)	$ 1,361