Subsequent Events (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Feb. 05, 2021	Dec. 31, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Funds held under reinsurance agreements, liability			$ 3,300,000,000	$ 3,200,000,000
Subsequent Event
Subsequent Event [Line Items]
Funds held under reinsurance agreements, liability		$ 690,000,000
Retroactive resinurance agreement, maximum		$ 1,000,000,000
Subsequent Event | Forecast
Subsequent Event [Line Items]
Reinsurance, loss on uncollectible accounts in period, amount	$ 12,000,000