Reinsurance and Indemnification - Aggregate Excess Catastrophe Florida and Southeast States Reinsurance Contract (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Reinsurance Retention Policy [Line Items]
Limit of aggregate losses under aggregate excess agreement	$ 3,400
Aggregate Excess Catastrophe Florida Reinsurance Contract
Reinsurance Retention Policy [Line Items]
Term of catastrophe reinsurance agreement contract	1 year
Retention percentage of reinsurance limit	80.00%
Limit of aggregate losses under aggregate excess agreement	$ 250