Financial Guaranty Insurance Contracts (Details 14) (USD $)					3 Months Ended											3 Months Ended		12 Months Ended		3 Months Ended		12 Months Ended		3 Months Ended		12 Months Ended		3 Months Ended		12 Months Ended
	Sep. 30, 2012		Dec. 31, 2011		Sep. 30, 2012 Variable rate demand obligations	Sep. 30, 2012 Variable rate demand obligations Minimum	Sep. 30, 2012 Variable rate demand obligations Maximum	Sep. 30, 2012 Financial Guaranty		Jun. 30, 2012 Financial Guaranty	Dec. 31, 2011 Financial Guaranty		Sep. 30, 2011 Financial Guaranty	Jun. 30, 2011 Financial Guaranty	Dec. 31, 2010 Financial Guaranty	Sep. 30, 2012 Financial Guaranty BIG 1 risk		Dec. 31, 2011 Financial Guaranty BIG 1 risk		Sep. 30, 2012 Financial Guaranty BIG 2 risk		Dec. 31, 2011 Financial Guaranty BIG 2 risk		Sep. 30, 2012 Financial Guaranty BIG 3 risk		Dec. 31, 2011 Financial Guaranty BIG 3 risk		Sep. 30, 2012 Financial Guaranty Below investment grade (BIG) risk		Dec. 31, 2011 Financial Guaranty Below investment grade (BIG) risk
Financial Guaranty Insurance BIG Transaction Loss Summary
Maximum Termination Payment Possible After Swap Obligations and Taking Account of Possible Rating Downgrade of Municipal Obligors	$ 370,000,000
Number of risks
Gross (in contracts)																148	[1]	171	[1]	90	[1]	71	[1]	136	[1]	126	[1]
Ceded (in contracts)																(56)	[1]	(68)	[1]	24	[1]	(26)	[1]	51	[1]	(48)	[1]
Total BIG, Net (in contracts)																												374	[1]	368	[1]
Total (in contracts)																												374	[1]	368	[1]
Remaining weighted average contract period
Gross (in years)																11 years 1 month 6 days		10 years		12 years		13 years 8 months 12 days		8 years 10 months 24 days		9 years 2 months 12 days
Ceded (in years)																9 years 3 months 18 days		9 years 2 months 12 days		15 years 7 months 6 days		20 years 6 months		6 years		6 years 4 months 24 days
Total BIG, Net (in years)																												10 years 7 months 6 days		10 years 4 months 24 days
Total (in years)																												10 years 7 months 2 days
Principal
Gross																8,410,000,000		9,675,000,000		3,390,000,000		3,732,000,000		7,854,000,000		7,831,000,000
Ceded																(1,467,000,000)		(1,378,000,000)		(157,000,000)		(274,000,000)		(555,000,000)		(627,000,000)
Total BIG, Net																												17,475,000,000		18,959,000,000
Total																												17,475,000,000		18,959,000,000
Interest
Gross																4,281,000,000		4,309,000,000		2,308,000,000		2,889,000,000		2,531,000,000		2,486,000,000
Ceded																(560,000,000)		(486,000,000)		(157,000,000)		(405,000,000)		(144,000,000)		(170,000,000)
Total BIG, Net																												8,259,000,000		8,623,000,000
Total																												8,259,000,000		8,623,000,000
Total net outstanding exposure
Gross																12,691,000,000	[2]	13,984,000,000	[2]	5,698,000,000	[2]	6,621,000,000	[2]	10,385,000,000	[2]	10,317,000,000	[2]
Ceded																(2,027,000,000)	[2]	(1,864,000,000)	[2]	(314,000,000)	[2]	(679,000,000)	[2]	(699,000,000)	[2]	(797,000,000)	[2]
Total BIG, Net																												25,734,000,000	[2]	27,582,000,000	[2]
Total																												25,734,000,000	[2]	27,582,000,000	[2]
Expected cash outflows (inflows)
Gross																1,661,000,000		1,731,000,000		1,041,000,000		1,833,000,000		3,052,000,000		2,423,000,000
Ceded																563,000,000		(659,000,000)		(97,000,000)		(121,000,000)		(136,000,000)		(133,000,000)
Total BIG, Net																												4,958,000,000		5,074,000,000
Effect of Consolidating FG VIEs																												(736,000,000)		998,000,000
Total																												4,222,000,000		4,076,000,000
Potential recoveries
Gross																(1,798,000,000)	[3]	(1,798,000,000)	[3]	(638,000,000)		(1,079,000,000)		2,541,000,000	[3]	(2,041,000,000)	[3]
Ceded																(576,000,000)		664,000,000	[3]	19,000,000	[3]	39,000,000	[3]	133,000,000	[3]	100,000,000	[3]
Total BIG, Net																												(4,249,000,000)	[3]	(4,115,000,000)	[3]
Effect of Consolidating FG VIEs																												741,000,000		1,060,000,000	[3]
Total																												(3,508,000,000)	[3]	(3,055,000,000)	[3]
Subtotal
Gross																(137,000,000)		(67,000,000)		403,000,000		754,000,000		511,000,000		382,000,000
Ceded																13,000,000		5,000,000		(78,000,000)		(82,000,000)		(3,000,000)		(33,000,000)
Total BIG, NET																												709,000,000		959,000,000
Effect of Consolidating FG VIEs																												5,000,000		62,000,000
Total																												714,000,000		1,021,000,000
Discount
Gross																61,000,000		16,000,000		(75,000,000)		(241,000,000)		(320,000,000)		(125,000,000)
Ceded																(3,000,000)		(5,000,000)		29,000,000		32,000,000		(3,000,000)		2,000,000
Total BIG, Net																												(311,000,000)		(321,000,000)
Effect of Consolidating FG VIEs																												76,000,000		45,000,000
Schedule of Insured Financial Obligations with Credit Deterioration, Reductions of Gross Claim Liability, Net Discount																												(235,000,000)		(276,000,000)
Present value of expected cash flows
Gross																(76,000,000)		(51,000,000)		328,000,000		513,000,000		191,000,000		257,000,000
Ceded																10,000,000		0		(49,000,000)		(50,000,000)		(6,000,000)		(31,000,000)
Total BIG, Net	398,000,000							398,000,000	[4]	826,000,000	638,000,000	[4]	773,000,000	713,000,000	409,000,000													398,000,000		638,000,000
Effect of Consolidating FG VIEs	(81,000,000)																											81,000,000		107,000,000
Total																												479,000,000		745,000,000
Deferred premium revenue
Gross																88,000,000		261,000,000		265,000,000		281,000,000		848,000,000		992,000,000
Ceded																(13,000,000)		(69,000,000)		(26,000,000)		(12,000,000)		(97,000,000)		(127,000,000)
Total BIG, Net																												1,065,000,000		1,326,000,000
Effect of Consolidating FG VIEs																												(315,000,000)		(391,000,000)
Total																												750,000,000		935,000,000
Reserves (salvage)
Gross																(115,000,000)	[5]	(97,000,000)	[5]	155,000,000	[5]	320,000,000		(42,000,000)	[5]	(110,000,000)	[5]
Ceded																15,000,000	[5]	7,000,000	[5]	(37,000,000)	[5]	(42,000,000)	[5]	14,000,000	[5]	7,000,000	[5]
Total BIG, Net																												(10,000,000)	[5]	85,000,000	[5]
Effect of consolidating FG VIEs	139,000,000		196,000,000																									139,000,000	[5]	196,000,000	[5]
Total	155,000,000	[6]	283,000,000	[6]				129,000,000			281,000,000																	129,000,000	[5]	281,000,000	[5]
Rate basis for bank bond rate					prime rate
Bank bond rate (as a percent)						2.00%	3.00%
Bank bond capped rate (as a percent)							25.00%
Threshold period of bonds held by bank for right of accelerated repayment (in days)						90 days	180 days
Accelerated repayment period for bank bonds (in years)						5 years	10 years
Financial Guaranty Insurance Contracts, Principal Amount BBB- or below					$ 800,000,000

[1] A risk represents the aggregate of the financial guaranty policies that share the same revenue source for purposes of making debt service payments. The ceded number of risks represents the number of risks for which the Company ceded a portion of its exposure.

[2] Includes BIG amounts related to FG VIEs which are not eliminated.

[3] Includes estimated future recoveries for breaches of R&W as well as excess spread, and draws on HELOCs.

[4] Includes expected LAE to be paid for mitigating claim liabilities of $26 million as of September 30, 2012 and $36 million as of December 31, 2011.

[5] See table “Components of net reserves (salvage).”

[6] See “Components of Net Reserves (Salvage)” table for loss and LAE reserve and salvage and subrogation recoverable components.