Employee Benefit Plans - Narrative (Details)	12 Months Ended
	Dec. 31, 2025 USD ($) plan	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 18,000,000	$ 17,000,000
Percentage within which the planned allocation is managed	5.00%
Net actuarial gain (loss)	$ (64,000,000)	107,000,000
Projected benefit obligation	186,000,000	186,000,000
Accumulated benefit obligation	179,000,000	178,000,000
Projected benefit obligation	0	0
Plan benefit accruals	$ 2,133,000,000	2,115,000,000
Growth-Oriented
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of pension plan assets	30.00%
Immunizing
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of pension plan assets	70.00%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0	0	$ 0
Expected contributions expected in the next fiscal year	0
Net actuarial gain (loss)	$ (64,000,000)	$ 107,000,000
Increase (decrease) in weighted average discount rate	(0.25%)	0.68%
Pre-tax (loss) gain to be amortized related to post-retirement obligations	$ (498,000,000)
Pension Plan | Quality Carriers, Inc. | Multiemployer Plan, Union-represented Employees
Defined Benefit Plan Disclosure [Line Items]
Number of multi-employer pension plans | plan	2
Contingent liability for full withdrawal or termination of multi-employer plan	$ 284,000,000
Pension Plan | Quality Carriers, Inc. | Multiemployer Plan, Union-represented Employees, Central Southeast and Southwest Areas Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Contingent liability for full withdrawal or termination of multi-employer plan	280,000,000
Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Plan benefit accruals	46,000,000	$ 49,000,000
Defined benefit plan, expected future benefit payments	42,000,000
Savings Plan
Defined Benefit Plan Disclosure [Line Items]
Expense associated with savings plans	$ 39,000,000	$ 40,000,000	$ 35,000,000