Reinsurance and Indemnification - 2019-1 PCS Excess Agreement (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) state
Ceded Credit Risk [Line Items]
Limit of aggregate losses under aggregate excess agreement	$ 3,400
2019-1 Excess Catastrophe Reinsurance Contract
Ceded Credit Risk [Line Items]
Number of states covered by reinsurance agreement | state	49
Retention percentage of reinsurance limit	75.00%
Retention amount for catastrophe reinsurance agreement contracts	$ 400
Retention amount annual limit	$ 2,750
Co-participation percentage	5.00%
Retention amount for catastrophe reinsurance agreement contracts, losses in excess	$ 3,070
Minimum | 2019-1 Excess Catastrophe Reinsurance Contract
Ceded Credit Risk [Line Items]
Retention amount for catastrophe reinsurance agreement contracts	3,540
Maximum | 2019-1 Excess Catastrophe Reinsurance Contract
Ceded Credit Risk [Line Items]
Retention amount for catastrophe reinsurance agreement contracts	$ 3,940