Reinsurance - Effect of Reinsurance on Statement of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Premiums Written:
Direct	$ 453	$ 663	$ 288
Assumed	1	14	324
Ceded	13	10	14
Net	467	687	626
Premiums Earned:
Direct	448	429	509
Assumed	41	54	51
Ceded	(4)	(7)	(12)
Net	485	476	548
Loss and LAE:
Direct	182	101	68
Assumed	24	2	(1)
Ceded	(3)	(10)	(3)
Net	$ 203	$ 93	$ 64