Reinsurance and Indemnification - Mandatory FHCF Contracts (Details) $ in Millions	7 Months Ended	12 Months Ended
	Dec. 31, 2019 USD ($) hurricane	Dec. 31, 2019 USD ($)
Reinsurance Retention Policy [Line Items]
Limit of aggregate losses under aggregate excess agreement		$ 3,400
Florida Excess Catastrophe Reinsurance Agreement
Reinsurance Retention Policy [Line Items]
Catastrophe reinsurance loss amount		$ 151
Catastrophe reinsurance aggregate, loss limit per contract year, percent		90.00%
Catastrophe reinsurance loss amount, placement		$ 136
Limit of aggregate losses under aggregate excess agreement	$ 54
Percent eligible for reimbursement		10.00%
Florida Excess Catastrophe Reinsurance Agreement, Two Largest Hurricanes
Reinsurance Retention Policy [Line Items]
Number of hurricanes | hurricane	2
Limit of aggregate losses under aggregate excess agreement	$ 54
Retention amount for catastrophe reinsurance agreement contracts	$ 18