Reinsurance and Indemnification - National Flood Insurance Program (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reinsurance Retention Policy [Line Items]
Property-liability insurance premiums earned	$ 1,982	$ 1,154	$ 1,136
National Flood Insurance Program
Reinsurance Retention Policy [Line Items]
Reinsurance and indemnification recoverables, net	34	30
Property-liability insurance premiums earned	350	261	258
Reinsurance ceded amount	$ 267	$ 87	$ 150