Business and Summary of Significant Accounting Policies - Trade and Notes Receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenue Recognition, Milestone Method [Line Items]
Insurance commissions as percentage of agent premiums	77.40%	76.90%	77.10%
Premium due from agents, net of accrued sales commissions	$ 40	$ 35
Minimum
Revenue Recognition, Milestone Method [Line Items]
Accrual for agency premiums reported within three months, percent	61.00%
Accrual for agency premiums reported within next three months, percent	7.00%
Accrual for agency premiums, remaining period	7 months
Maximum
Revenue Recognition, Milestone Method [Line Items]
Accrual for agency premiums reported within three months, percent	92.00%
Accrual for agency premiums reported within next three months, percent	29.00%
Accrual for agency premiums, remaining period	15 months