Benefit Plans (Schedule of Non-Service Cost (Benefit) Presented in the Consolidated Statement of Operations) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic defined benefits expense (reversal of expense), excluding service cost component	$ (3)	$ 3	$ (8)	$ 3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]			Other operating expenses, Insurance claims and policyholders’ benefits (re-measurement loss of $36, $48, $59 and $88)
Pension settlement transaction loss	0	4	$ 0	4
Pension settlement transaction gain (loss), net of tax				(3)
Insurance claims and policyholder's benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic defined benefits expense (reversal of expense), excluding service cost component	(1)	1	(2)	1
Other operating expenses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic defined benefits expense (reversal of expense), excluding service cost component	$ (2)	$ 2	$ (6)	$ 2

CNA FINANCIAL CORP 10-Q