Reinsurance and Other Monoline Exposures - Effect of Reinsurance on Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Premiums Written:
Direct	$ 73	$ 109
Assumed	0	2
Ceded	(11)	11
Net	62	122
Premiums Earned:
Direct	143	167
Assumed	5	6
Ceded	(3)	(9)
Net	145	164
Loss and LAE:
Direct	(14)	67
Assumed	(3)	3
Ceded	(1)	(11)
Net	$ (18)	$ 59