Consolidated Statements Of Operations (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Change in fair value of insured derivatives:
Unrealized gains (losses) on insured derivatives	$ (441)		$ (607)		$ 1,650
Investment losses related to other-than-temporary impairments:
Net gains (losses) on extinguishment of debt	26		60		269
Total revenues	(1,557)		894		2,954
Expenses:
Total expenses	682		989		1,737
Income (loss) before income taxes	(2,239)		(95)		1,217
Provision (benefit) for income taxes	(920)		(148)		583
Net income (loss)	(1,319)		53		634
Preferred stock dividends of subsidiary					11
Net income (loss) available to common shareholders	(1,319)		53		623
Net income (loss) per common share:
Basic	$ (6.69)		$ 0.26		$ 2.99
Diluted	$ (6.69)		$ 0.26		$ 2.99
Weighted average number of common shares outstanding:
Basic	197,019,968	[1]	202,421,433	[1]	208,156,622	[1]
Diluted	197,019,968		203,021,134		208,156,622
Non Variable Interest Entities [Member]
Premiums earned:
Scheduled premiums earned	456		504		609
Refunding premiums earned	149		90		137
Premiums earned (net of ceded premiums of $12, $28, and $87)	605		594		746
Net investment income	383		457		568
Fees and reimbursements	50		160		146
Change in fair value of insured derivatives:
Realized gains (losses) and other settlements on insured derivatives	(2,371)		(162)		(166)
Unrealized gains (losses) on insured derivatives	(441)		(607)		1,650
Net change in fair value of insured derivatives	(2,812)		(769)		1,484
Net gains (losses) on financial instruments at fair value and foreign exchange	(99)		88		225
Investment losses related to other-than-temporary impairments:
Investment losses related to other-than-temporary impairments	(125)		(206)		(531)
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)	24		142		170
Net investment losses related to other-than-temporary impairments	(101)		(64)		(361)
Net gains (losses) on extinguishment of debt	26		35		225
Other net realized gains (losses)	(1)		29		(60)
Expenses:
Losses and loss adjustment	(80)		232		864
Amortization of deferred acquisition costs	63		59		82
Operating	308		290		315
Interest	300		325		374
Variable Interest Entities [Member]
Premiums earned:
Net investment income	70		73		88
Change in fair value of insured derivatives:
Net gains (losses) on financial instruments at fair value and foreign exchange	59		342		(4)
Investment losses related to other-than-temporary impairments:
Investment losses related to other-than-temporary impairments					(275)
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)					169
Net investment losses related to other-than-temporary impairments					(106)
Net gains (losses) on extinguishment of debt			25		44
Other net realized gains (losses)	263		(76)		(41)
Expenses:
Operating	29		24		1
Interest	$ 62		$ 59		$ 101

[1] Includes 5,080,742, 5,325,428 and 5,259,561 of unvested restricted stock and units that receive nonforfeitable dividends or dividend equivalents for the years ended December 31, 2011, 2010 and 2009, respectively.