Consolidated Statements Of Operations - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Change in fair value of insured derivatives:
Unrealized gains (losses) on insured derivatives			$ 36	$ (10)
Net change in fair value of insured derivatives	$ (1)	$ (1)	(13)	(51)
Net gains (losses) on financial instruments at fair value and foreign exchange	5	(11)	18	(55)
Net investment losses related to other-than-temporary impairments:
Net investment losses related to other-than-temporary impairments	(1)	(71)	(3)	(84)
Net gains (losses) on extinguishment of debt	3	1	3	9
Other net realized gains (losses)	1	(1)	0	36
Total revenues	105	33	190	182
Expenses:
Losses and loss adjustment	46	205	177	469
Interest	52	50	155	148
Total expenses	150	306	477	785
Income (loss) before income taxes	(45)	(273)	(287)	(603)
Provision (benefit) for income taxes	0	(6)	2	965
Net income (loss)	$ (45)	$ (267)	$ (289)	$ (1,568)
Net income (loss) per common share:
Basic	$ (0.5)	$ (2.17)	$ (3.24)	$ (12.38)
Diluted	$ (0.5)	$ (2.17)	$ (3.24)	$ (12.38)
Weighted average number of common shares outstanding:
Basic	89,490,267	122,967,924	89,075,892	126,643,642
Diluted	89,490,267	122,967,924	89,075,892	126,643,642
Non Variable Interest Entity [Member]
Premiums earned:
Scheduled premiums earned	$ 44	$ 26	$ 96	$ 82
Refunding premiums earned	18	27	42	64
Premiums earned (net of ceded premiums of $1, $1, $4 and $4)	62	53	138	146
Net investment income	31	33	96	122
Fees and reimbursements	17	1	23	9
Change in fair value of insured derivatives:
Realized gains (losses) and other settlements on insured derivatives	(5)	(7)	(49)	(41)
Unrealized gains (losses) on insured derivatives	4	6	36	(10)
Net change in fair value of insured derivatives	(1)	(1)	(13)	(51)
Net gains (losses) on financial instruments at fair value and foreign exchange	5	(11)	18	(55)
Net investment losses related to other-than-temporary impairments:
Investment losses related to other-than-temporary impairments	0	(26)	0	(80)
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)	(1)	(45)	(3)	(4)
Net investment losses related to other-than-temporary impairments	(1)	(71)	(3)	(84)
Net gains (losses) on extinguishment of debt	3	1	3	9
Other net realized gains (losses)	1	(1)	0	36
Expenses:
Losses and loss adjustment	46	205	177	469
Amortization of deferred acquisition costs	9	8	17	23
Operating	18	21	57	82
Interest	52	50	155	148
Variable Interest Entity Primary Beneficiary [Member]
Premiums earned:
Net investment income	9	8	25	20
Change in fair value of insured derivatives:
Net gains (losses) on financial instruments at fair value and foreign exchange	12	21	29	2
Net investment losses related to other-than-temporary impairments:
Other net realized gains (losses)	(33)	0	(126)	28
Expenses:
Operating	3	3	8	8
Interest	$ 22	$ 19	$ 63	$ 55