Consolidated Statements Of Operations (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Change in fair value of insured derivatives:
Unrealized gains (losses) on insured derivatives	$ 73		$ (303)
Investment losses related to other-than-temporary impairments:
Net gains (losses) on extinguishment of debt	4
Total revenues	219		383
Expenses:
Losses and loss adjustment	(194)
Total expenses	4		362
Income (loss) before income taxes	215		21
Provision (benefit) for income taxes	51		11
Net income (loss)	164		10
Net income (loss) per common share:
Basic	$ 0.84		$ 0.05
Diluted	$ 0.84		$ 0.05
Weighted average number of common shares outstanding:
Basic	194,523,933	[1]	193,489,424	[1]
Diluted	195,631,960		194,594,974
Non Variable Interest Entities [Member]
Premiums earned:
Scheduled premiums earned	79		96
Refunding premiums earned	41		41
Premiums earned (net of ceded premiums of $2 and $3)	120		137
Net investment income	38		62
Fees and reimbursements	6		7
Change in fair value of insured derivatives:
Realized gains (losses) and other settlements on insured derivatives	12		(4)
Unrealized gains (losses) on insured derivatives	(73)		303
Net change in fair value of insured derivatives	(61)		299
Net gains (losses) on financial instruments at fair value and foreign exchange	63		(19)
Investment losses related to other-than-temporary impairments:
Investment losses related to other-than-temporary impairments			(53)
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)			(41)
Net investment losses related to other-than-temporary impairments			(94)
Net gains (losses) on extinguishment of debt	4
Other net realized gains (losses)			1
Expenses:
Losses and loss adjustment	(194)		97
Amortization of deferred acquisition costs	16		13
Operating	106		158
Interest	60		73
Variable Interest Entity [Member]
Premiums earned:
Net investment income	16		17
Change in fair value of insured derivatives:
Net gains (losses) on financial instruments at fair value and foreign exchange	33		(27)
Expenses:
Operating	4		6
Interest	$ 12		$ 15

[1] Includes 6,125,599 and 5,219,053 of unvested restricted stock and units that receive nonforfeitable dividends or dividend equivalents for the three months ended March 31, 2013 and 2012, respectively.