Reinsurance and Indemnification - Florida Hurricane Catastrophe Fund (Details)	12 Months Ended
	May 31, 2022 USD ($) hurricane	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2013 USD ($)
Reinsurance Retention Policy [Line Items]
Property-liability insurance premiums earned		$ 1,982,000,000	$ 1,154,000,000	$ 1,136,000,000
Florida Hurricane Catastrophe Fund
Reinsurance Retention Policy [Line Items]
Emergency assessment maximum percentage of premiums first year		6.00%
Emergency assessment maximum percentage of premiums subsequent years		10.00%
Emergency assessment, bonds issued					$ 2,000,000,000
Emergency assessment maximum percentage of premiums subsequent years, FL OIR		0.00%
Florida Hurricane Catastrophe Fund
Reinsurance Retention Policy [Line Items]
Property-liability insurance premiums earned		$ 15,000,000	9,000,000	9,000,000
Reinsurance recoverable, qualifying losses, amount		13,000,000	15,000,000	$ 33,000,000
Reinsurance and indemnification recoverables, net		$ 25,000,000	$ 32,000,000
Florida Hurricane Catastrophe Fund | Forecast
Reinsurance Retention Policy [Line Items]
Percent of losses in excess of retention level to be reimbursed	90.00%
Retention level for losses related to 2 largest hurricanes	$ 104,000,000
Number of storms | hurricane	2
Retention level for losses related to other hurricanes	$ 35,000,000
Maximum Retention level for losses related to hurricanes	$ 251,000,000