Consolidated Statements Of Operations - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in fair value of insured derivatives:
Unrealized gains (losses) on insured derivatives		$ 7	$ 25	$ 31
Net change in fair value of insured derivatives		6	15	(25)
Net gains (losses) on financial instruments at fair value and foreign exchange		(38)	52	(17)
Net investment losses related to other-than-temporary impairments:
Net investment losses related to other-than-temporary impairments			(67)	(5)
Net gains (losses) on extinguishment of debt			(1)	3
Other net realized gains (losses)		0	4	0
Total revenues		282	280	162
Expenses:
Losses and loss adjustment		530	242	63
Interest		178	201	206
Total expenses		860	637	458
Income (loss) before income taxes		(578)	(357)	(296)
Provision (benefit) for income taxes		0	2	0
Net income (loss)		$ (578)	$ (359)	$ (296)
Net income (loss) per common share:
Basic		$ (9.78)	$ (4.43)	$ (3.33)
Diluted		$ (9.78)	$ (4.43)	$ (3.33)
Weighted average number of common shares outstanding:
Basic	[1]	59,071,843	81,014,285	89,013,711
Diluted		59,071,843	81,014,285	89,013,711
Non Variable Interest Entity [Member]
Premiums earned:
Scheduled premiums earned		$ 59	$ 68	$ 114
Refunding premiums earned		14	17	48
Premiums earned (net of ceded premiums of $5, $5 and $5)		73	85	162
Net investment income		76	114	130
Fees and reimbursements		2	1	25
Change in fair value of insured derivatives:
Realized gains (losses) and other settlements on insured derivatives		(1)	(10)	(56)
Unrealized gains (losses) on insured derivatives		7	25	31
Net change in fair value of insured derivatives		6	15	(25)
Net gains (losses) on financial instruments at fair value and foreign exchange		(38)	52	(17)
Net investment losses related to other-than-temporary impairments:
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)		0	(67)	(5)
Net investment losses related to other-than-temporary impairments		0	(67)	(5)
Net gains (losses) on extinguishment of debt		0	(1)	3
Other net realized gains (losses)		0	4	0
Expenses:
Losses and loss adjustment		530	242	63
Amortization of deferred acquisition costs		10	11	20
Operating		87	92	71
Interest		178	201	206
Variable Interest Entity Primary Beneficiary [Member]
Premiums earned:
Net investment income		18	34	35
Change in fair value of insured derivatives:
Net gains (losses) on financial instruments at fair value and foreign exchange		108	105	25
Net investment losses related to other-than-temporary impairments:
Other net realized gains (losses)		37	(62)	(171)
Expenses:
Operating		5	9	11
Interest		$ 50	$ 82	$ 87

[1] Includes 0.9 million, 1.0 million and 0.8 million of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend equivalents for the years ended December 31, 2020, 2019 and 2018, respectively.