Business and Summary of Significant Accounting Policies - Trade and Notes Receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue Recognition, Milestone Method [Line Items]
Insurance commissions as percentage of agent premiums	76.70%	76.40%	76.30%
Premium due from agents, net of accrued sales commissions	$ 113	$ 65
Minimum
Revenue Recognition, Milestone Method [Line Items]
Accrual for agency premiums, time lag period	7 months
Accrual for agency premiums reported within three Months, percent	69.00%
Accrual for agency premiums reported within next three months, percent	14.00%
Maximum
Revenue Recognition, Milestone Method [Line Items]
Accrual for agency premiums, time lag period	15 months
Accrual for agency premiums reported within three Months, percent	84.00%
Accrual for agency premiums reported within next three months, percent	26.00%