Financial Guaranty Contracts Accounted for as Credit Derivatives (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Distribution of Credit Derivative Net Par Outstanding
Premiums Receivable, at Carrying Value	$ 1,005	[1]	$ 1,003	[1]	$ 1,168	[1]	$ 1,418
Premium written, net	211		245		347
Net Par Outstanding	70,781		85,047
Percentage of total	100.00%		100.00%
Original Subordination (as a percent)	0.00%	[2]
Current Subordination (as a percent)	0.00%	[2]	0.00%	[2]
Net unrealized gains (losses)	(477)		554		(155)
Financial Guarantee Insurance Contracts, Premium Receivable, Premium Payments Received	294		318		487
U.S. RMBS
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	7,257		8,532
Original Subordination (as a percent)	24.20%	[2],[3]	24.10%	[2]
Current Subordination (as a percent)	30.40%	[2],[3]	32.20%	[2]
Net unrealized gains (losses)	(551)		381		(301)
U.S. RMBS | 2004 and Prior
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	124
Original Subordination (as a percent)	6.40%	[3]
Current Subordination (as a percent)	19.20%	[3]
Net unrealized gains (losses)	3
U.S. RMBS | 2005
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	2,036
Original Subordination (as a percent)	31.20%	[3]
Current Subordination (as a percent)	66.30%	[3]
Net unrealized gains (losses)	12
U.S. RMBS | Vintage 2006 [Member]
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	1,572
Original Subordination (as a percent)	29.40%	[3]
Current Subordination (as a percent)	34.50%	[3]
Net unrealized gains (losses)	(63)
U.S. RMBS | Vintage 2007 [Member]
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	3,525
Original Subordination (as a percent)	18.50%	[3]
Current Subordination (as a percent)	8.20%	[3]
Net unrealized gains (losses)	(503)
CMBS
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	4,094		4,612
Original Subordination (as a percent)	33.30%	[2]	32.60%	[2]
Current Subordination (as a percent)	41.80%	[2]	38.90%	[2]
Net unrealized gains (losses)	2		11		10
Super senior
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	18,908		21,802
Percentage of total	26.70%		25.60%
AAA
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	32,010		40,240
Percentage of total	45.20%		47.30%
AA
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	3,083		4,342
Percentage of total	4.40%		5.10%
A
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	5,487		5,830
Percentage of total	7.80%		6.90%
BBB
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	4,584		5,030
Percentage of total	6.40%		5.90%
Below investment grade (BIG)
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	$ 6,709		$ 7,803
Percentage of total	9.50%		9.20%

[1] 2)Excludes $29 million, $28 million and $23 million as of December 31, 2012 , 2011 and 2010, respectively, related to consolidated FG VIEs.

[2] Represents the sum of subordinate tranches and over-collateralization and does not include any benefit from excess interest collections that may be used to absorb losses.

[3] Represents the sum of subordinate tranches and overcollateralization and does not include any benefit from excess interest collections that may be used to absorb losses.