Consolidated Statements Of Operations (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Premiums earned:
Premiums earned (net of ceded premiums of $12, $10 and $14)	$ 397		$ 457		$ 605
Change in fair value of insured derivatives:
Unrealized gains (losses) on insured derivatives	903		1,777		1,870
Net change in fair value of insured derivatives	459		232		1,464
Net gains (losses) on financial instruments at fair value and foreign exchange	78		69		55
Investment losses related to other-than-temporary impairments:
Net investment losses related to other-than-temporary impairments	(15)				(105)
Net gains (losses) on extinguishment of debt	3		60
Other net realized gains (losses)	28		(29)		7
Total revenues	1,270		1,209		2,435
Expenses:
Losses and loss adjustment	133		117		50
Interest	210		236		284
Total expenses	629		793		837
Income (loss) before income taxes	641		416		1,598
Provision (benefit) for income taxes	72		166		364
Net income (loss)	569		250		1,234
Net income (loss) per common share:
Net income (loss) per basic common share	$ 2.94		$ 1.3		$ 6.36
Net income (loss) per diluted common share	$ 2.76		$ 1.29		$ 6.33
Weighted average number of common shares outstanding:
Basic	188,171,503	[1]	189,071,011	[1]	188,834,626	[1]
Diluted	190,898,627		190,312,913		189,897,021
Non Variable Interest Entity [Member]
Premiums earned:
Scheduled premiums earned	258		304		372
Refunding premiums earned	139		153		233
Premiums earned (net of ceded premiums of $12, $10 and $14)	397		457		605
Net investment income	179		166		214
Fees and reimbursements	40		21		61
Change in fair value of insured derivatives:
Realized gains (losses) and other settlements on insured derivatives	(444)		(1,545)		(406)
Unrealized gains (losses) on insured derivatives	903		1,777		1,870
Net change in fair value of insured derivatives	459		232		1,464
Net gains (losses) on financial instruments at fair value and foreign exchange	78		69		55
Investment losses related to other-than-temporary impairments:
Investment losses related to other-than-temporary impairments	(99)		0		(58)
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)	84		0		(47)
Net investment losses related to other-than-temporary impairments	(15)		0		(105)
Net gains (losses) on extinguishment of debt	3		60		0
Other net realized gains (losses)	28		(29)		7
Expenses:
Losses and loss adjustment	133		117		50
Amortization of deferred acquisition costs	44		46		50
Operating	195		338		381
Interest	210		236		284
Variable Interest Entity Primary Beneficiary [Member]
Premiums earned:
Net investment income	50		56		67
Change in fair value of insured derivatives:
Net gains (losses) on financial instruments at fair value and foreign exchange	50		175		18
Investment losses related to other-than-temporary impairments:
Net gains (losses) on extinguishment of debt	4		1		49
Other net realized gains (losses)	(3)		1		0
Expenses:
Operating	8		11		17
Interest	$ 39		$ 45		$ 55

[1] Includes 412,769, 629,896 and 506,714 of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend equivalents for the years ended December 31, 2014, 2013 and 2012, respectively.