Basis of Presentation - Adoption on Segment Results of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance claims and policyholders’ benefits	$ 1,653	$ 1,478
Income before income tax	519	439
Income tax expense	(115)	(87)
Net income	404	352
Amounts attributable to noncontrolling interests	(29)	(30)
Net income attributable to Loews Corporation	375	322
Re-measurement gain of insurance claims and policyholders’ benefits	$ 1	5
CNA Financial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance claims and policyholders’ benefits		1,478
Income before income tax		355
Income tax expense		(60)
Net income		295
Amounts attributable to noncontrolling interests		(30)
Net income attributable to Loews Corporation		265
As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance claims and policyholders’ benefits		1,455
Income before income tax		462
Income tax expense		(92)
Net income		370
Amounts attributable to noncontrolling interests		(32)
Net income attributable to Loews Corporation		338
As Reported | CNA Financial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance claims and policyholders’ benefits		1,455
Income before income tax		378
Income tax expense		(65)
Net income		313
Amounts attributable to noncontrolling interests		(32)
Net income attributable to Loews Corporation		281
Effect of Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance claims and policyholders’ benefits		23
Income before income tax		(23)
Income tax expense		5
Net income		(18)
Amounts attributable to noncontrolling interests		2
Net income attributable to Loews Corporation		(16)
Effect of Adoption | CNA Financial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Insurance claims and policyholders’ benefits		23
Income before income tax		(23)
Income tax expense		5
Net income		(18)
Amounts attributable to noncontrolling interests		2
Net income attributable to Loews Corporation		$ (16)