Outstanding Exposure - Financial Guaranty Exposures and Below-Investment-Grade Credits (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Financial guarantee obligations
Net Par Amount Outstanding	$ 449,625		$ 459,107
Financial Guaranty Contracts Accounted for as Credit Derivatives Outstanding Principal Amount	51,318		54,482
Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	21,943		22,538
% of Total Net Par Outstanding	4.90%		4.90%
Financial Guaranty Contracts Accounted for as Insurance Outstanding Principal Amount	17,367	[1]	17,745	[1]
Financial Guaranty Contracts Accounted for as Credit Derivatives Outstanding Principal Amount	4,576		4,793
Financial Guaranty Contracts Accounted for as Insurance Number of Contracts	382	[1],[2]	384	[1],[2]
Financial Guaranty Contracts Accounted for as Credit Derivatives Number of Contracts	72	[2]	73	[2]
Insured Financial Obligations Number of Contracts	454	[2]	457	[2]
Category 1
Financial guarantee obligations
Net Par Amount Outstanding	14,250		14,751
Category 1 | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	14,250		14,751
Financial Guaranty Contracts Accounted for as Insurance Outstanding Principal Amount	12,242	[1]	12,391	[1]
Financial Guaranty Contracts Accounted for as Credit Derivatives Outstanding Principal Amount	2,008		2,360
Financial Guaranty Contracts Accounted for as Insurance Number of Contracts	193	[1],[2]	185	[1],[2]
Financial Guaranty Contracts Accounted for as Credit Derivatives Number of Contracts	24	[2]	25	[2]
Insured Financial Obligations Number of Contracts	217	[2]	210	[2]
Category 2
Financial guarantee obligations
Net Par Amount Outstanding	3,721		3,949
Category 2 | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	3,721		3,949
Financial Guaranty Contracts Accounted for as Insurance Outstanding Principal Amount	2,253	[1]	2,323	[1]
Financial Guaranty Contracts Accounted for as Credit Derivatives Outstanding Principal Amount	1,468		1,626
Financial Guaranty Contracts Accounted for as Insurance Number of Contracts	80	[1],[2]	80	[1],[2]
Financial Guaranty Contracts Accounted for as Credit Derivatives Number of Contracts	21	[2]	21	[2]
Insured Financial Obligations Number of Contracts	101	[2]	101	[2]
Category 3
Financial guarantee obligations
Net Par Amount Outstanding	3,972		3,838
Category 3 | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	3,972		3,838
Financial Guaranty Contracts Accounted for as Insurance Outstanding Principal Amount	2,872	[1]	3,031	[1]
Financial Guaranty Contracts Accounted for as Credit Derivatives Outstanding Principal Amount	1,100		807
Financial Guaranty Contracts Accounted for as Insurance Number of Contracts	109	[1],[2]	119	[1],[2]
Financial Guaranty Contracts Accounted for as Credit Derivatives Number of Contracts	27	[2]	27	[2]
Insured Financial Obligations Number of Contracts	136	[2]	146	[2]
Prime first lien
Financial guarantee obligations
Net Par Amount Outstanding	528		541
Financial Guaranty Contracts Accounted for as Credit Derivatives Outstanding Principal Amount	258
Prime first lien | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	395		403
% of Total Net Par Outstanding	0.10%		0.10%
Prime first lien | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	77		52
Prime first lien | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	289		321
Prime first lien | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	29		30
Alt-A first lien
Financial guarantee obligations
Net Par Amount Outstanding	3,478		3,590
Alt-A first lien | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	2,713		2,728
% of Total Net Par Outstanding	0.60%		0.60%
Alt-A first lien | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	703		656
Alt-A first lien | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	787		1,137
Alt-A first lien | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	1,223		935
Option ARM
Financial guarantee obligations
Net Par Amount Outstanding	877		937
Option ARM | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	565		598
% of Total Net Par Outstanding	0.10%		0.10%
Option ARM | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	66		71
Option ARM | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	59		60
Option ARM | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	440		467
Subprime
Financial guarantee obligations
Net Par Amount Outstanding	5,921		6,130
Financial Guaranty Contracts Accounted for as Credit Derivatives Outstanding Principal Amount	2,837
Subprime | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	1,856		1,945
% of Total Net Par Outstanding	0.40%		0.40%
Subprime | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	227		297
Subprime | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	860		908
Subprime | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	769		740
Close ended second lien
Financial guarantee obligations
Net Par Amount Outstanding	239		244
Close ended second lien | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	143		146
% of Total Net Par Outstanding	0.00%		0.00%
Close ended second lien | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	8		8
Close ended second lien | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	19		20
Close ended second lien | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	116		118
HELOCs
Financial guarantee obligations
Net Par Amount Outstanding	1,982		2,279
HELOCs | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	1,734		1,897
% of Total Net Par Outstanding	0.40%		0.40%
HELOCs | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	1,480		1,499
HELOCs | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	19		20
HELOCs | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	235		378
U.S. RMBS
Financial guarantee obligations
Net Par Amount Outstanding	13,025		13,721
Financial Guaranty Contracts Accounted for as Credit Derivatives Outstanding Principal Amount	5,637
U.S. RMBS | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	7,406		7,717
% of Total Net Par Outstanding	1.60%		1.60%
U.S. RMBS | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	2,561		2,583
U.S. RMBS | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	2,033		2,466
U.S. RMBS | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	2,812		2,668
TruPS
Financial guarantee obligations
Net Par Amount Outstanding	4,826		4,970
TruPS | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	1,578		1,722
% of Total Net Par Outstanding	0.40%		0.40%
TruPS | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	1,235		1,587
TruPS | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	343		135
TruPS | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	0		0
Other structured finance
Financial guarantee obligations
Net Par Amount Outstanding	50,520		54,237
Other structured finance | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	2,371		2,397
% of Total Net Par Outstanding	0.50%		0.50%
Other structured finance | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	1,348		1,367
Other structured finance | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	304		309
Other structured finance | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	719		721
Public Finance U.S.
Financial guarantee obligations
Net Par Amount Outstanding	346,428		352,181
Public Finance U.S. | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	8,977		9,094
% of Total Net Par Outstanding	2.00%		2.00%
Public Finance U.S. | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	8,117		8,205
Public Finance U.S. | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	419		440
Public Finance U.S. | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	441		449
Public Finance Non-U.S.
Financial guarantee obligations
Net Par Amount Outstanding	34,826		33,998
Public Finance Non-U.S. | Below investment grade (BIG)
Financial guarantee obligations
Net Par Amount Outstanding	1,611		1,608
% of Total Net Par Outstanding	0.40%		0.40%
Public Finance Non-U.S. | Category 1
Financial guarantee obligations
Net Par Amount Outstanding	989		1,009
Public Finance Non-U.S. | Category 2
Financial guarantee obligations
Net Par Amount Outstanding	622		599
Public Finance Non-U.S. | Category 3
Financial guarantee obligations
Net Par Amount Outstanding	$ 0		$ 0

[1] Includes net par outstanding for FG VIEs.

[2] A risk represents the aggregate of the financial guaranty policies that share the same revenue source for purposes of making Debt Service payments.