Outstanding Exposure - Financial Guaranty Portfolio by Asset Class (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Guarantor Obligations [Line Items]
Gross Par Outstanding	$ 487,895		$ 550,907
Ceded Par Amount	28,788	[1]	32,135
Net Par Outstanding (excluding loss mitigation bonds)	459,107	[2]	518,772	[2]
Public Finance U.S.
Guarantor Obligations [Line Items]
Gross Par Outstanding	367,616		404,880
Ceded Par Amount	15,435		16,951
Net Par Outstanding (excluding loss mitigation bonds)	352,181	[2]	387,929	[2]
Public Finance U.S. | General obligation
Guarantor Obligations [Line Items]
Gross Par Outstanding	160,751		175,932
Ceded Par Amount	5,474		5,947
Net Par Outstanding (excluding loss mitigation bonds)	155,277		169,985
Public Finance U.S. | Tax backed
Guarantor Obligations [Line Items]
Gross Par Outstanding	70,552		77,894
Ceded Par Amount	3,728		4,145
Net Par Outstanding (excluding loss mitigation bonds)	66,824		73,749
Public Finance U.S. | Municipal utilities
Guarantor Obligations [Line Items]
Gross Par Outstanding	57,893		63,933
Ceded Par Amount	1,569		1,817
Net Par Outstanding (excluding loss mitigation bonds)	56,324		62,116
Public Finance U.S. | Transportation
Guarantor Obligations [Line Items]
Gross Par Outstanding	32,514		35,624
Ceded Par Amount	1,684		1,825
Net Par Outstanding (excluding loss mitigation bonds)	30,830		33,799
Public Finance U.S. | Healthcare
Guarantor Obligations [Line Items]
Gross Par Outstanding	17,663		19,507
Ceded Par Amount	1,531		1,669
Net Par Outstanding (excluding loss mitigation bonds)	16,132		17,838
Public Finance U.S. | Higher education
Guarantor Obligations [Line Items]
Gross Par Outstanding	14,470		16,244
Ceded Par Amount	399		474
Net Par Outstanding (excluding loss mitigation bonds)	14,071		15,770
Public Finance U.S. | Infrastructure finance
Guarantor Obligations [Line Items]
Gross Par Outstanding	5,014		5,100
Ceded Par Amount	900		890
Net Par Outstanding (excluding loss mitigation bonds)	4,114		4,210
Public Finance U.S. | Housing
Guarantor Obligations [Line Items]
Gross Par Outstanding	3,518		4,792
Ceded Par Amount	132		159
Net Par Outstanding (excluding loss mitigation bonds)	3,386		4,633
Public Finance U.S. | Investor-owned utilities
Guarantor Obligations [Line Items]
Gross Par Outstanding	992		1,070
Ceded Par Amount	1		1
Net Par Outstanding (excluding loss mitigation bonds)	991		1,069
Public Finance U.S. | Other public finance—U.S.
Guarantor Obligations [Line Items]
Gross Par Outstanding	4,249		4,784
Ceded Par Amount	17		24
Net Par Outstanding (excluding loss mitigation bonds)	4,232		4,760
Public Finance Non-U.S.
Guarantor Obligations [Line Items]
Gross Par Outstanding	42,274		46,304
Ceded Par Amount	8,276		8,764
Net Par Outstanding (excluding loss mitigation bonds)	33,998	[2]	37,540	[2]
Public Finance Non-U.S. | Infrastructure finance
Guarantor Obligations [Line Items]
Gross Par Outstanding	17,373		18,716
Ceded Par Amount	2,670		2,904
Net Par Outstanding (excluding loss mitigation bonds)	14,703		15,812
Public Finance Non-U.S. | Regulated utilities
Guarantor Obligations [Line Items]
Gross Par Outstanding	15,502		16,861
Ceded Par Amount	4,297		4,367
Net Par Outstanding (excluding loss mitigation bonds)	11,205		12,494
Public Finance Non-U.S. | Pooled infrastructure
Guarantor Obligations [Line Items]
Gross Par Outstanding	2,754		3,430
Ceded Par Amount	234		230
Net Par Outstanding (excluding loss mitigation bonds)	2,520		3,200
Public Finance Non-U.S. | Other public finance—U.S.
Guarantor Obligations [Line Items]
Gross Par Outstanding	6,645		7,297
Ceded Par Amount	1,075		1,263
Net Par Outstanding (excluding loss mitigation bonds)	5,570		6,034
Public Finance
Guarantor Obligations [Line Items]
Gross Par Outstanding	409,890		451,184
Ceded Par Amount	23,711		25,715
Net Par Outstanding (excluding loss mitigation bonds)	386,179		425,469
Structured Finance U.S.
Guarantor Obligations [Line Items]
Gross Par Outstanding	62,591		79,189
Ceded Par Amount	3,684		4,654
Net Par Outstanding (excluding loss mitigation bonds)	58,907	[2]	74,535	[2]
Structured Finance U.S. | Other public finance—U.S.
Guarantor Obligations [Line Items]
Gross Par Outstanding	2,067		2,307
Ceded Par Amount	1,080		1,128
Net Par Outstanding (excluding loss mitigation bonds)	987		1,179
Structured Finance U.S. | Pooled corporate obligations
Guarantor Obligations [Line Items]
Gross Par Outstanding	32,955		44,120
Ceded Par Amount	1,630		2,234
Net Par Outstanding (excluding loss mitigation bonds)	31,325		41,886
Structured Finance U.S. | Residential mortgage-backed security (RMBS)
Guarantor Obligations [Line Items]
Gross Par Outstanding	14,542		18,114
Ceded Par Amount	821		1,079
Net Par Outstanding (excluding loss mitigation bonds)	13,721		17,035
Structured Finance U.S. | Commercial mortgage-backed securities (CMBS) and other commercial real estate related exposures
Guarantor Obligations [Line Items]
Gross Par Outstanding	3,990		4,293
Ceded Par Amount	38		46
Net Par Outstanding (excluding loss mitigation bonds)	3,952		4,247
Structured Finance U.S. | Insurance securitizations
Guarantor Obligations [Line Items]
Gross Par Outstanding	3,082		2,991
Ceded Par Amount	47		48
Net Par Outstanding (excluding loss mitigation bonds)	3,035		2,943
Structured Finance U.S. | Financial product
Guarantor Obligations [Line Items]
Gross Par Outstanding	2,709		3,653
Ceded Par Amount	0		0
Net Par Outstanding (excluding loss mitigation bonds)	2,709		3,653
Structured Finance U.S. | Consumer receivables
Guarantor Obligations [Line Items]
Gross Par Outstanding	2,257		2,429
Ceded Par Amount	59		60
Net Par Outstanding (excluding loss mitigation bonds)	2,198		2,369
Structured Finance U.S. | Commercial receivables
Guarantor Obligations [Line Items]
Gross Par Outstanding	918		1,033
Ceded Par Amount	7		8
Net Par Outstanding (excluding loss mitigation bonds)	911		1,025
Structured Finance U.S. | Structured credit
Guarantor Obligations [Line Items]
Gross Par Outstanding	71		249
Ceded Par Amount	2		51
Net Par Outstanding (excluding loss mitigation bonds)	69		198
Structured Finance Non-U.S.
Guarantor Obligations [Line Items]
Gross Par Outstanding	15,414		20,534
Ceded Par Amount	1,393		1,766
Net Par Outstanding (excluding loss mitigation bonds)	14,021		18,768
Structured Finance Non-U.S. | Other public finance—U.S.
Guarantor Obligations [Line Items]
Gross Par Outstanding	403		402
Ceded Par Amount	25		25
Net Par Outstanding (excluding loss mitigation bonds)	378		377
Structured Finance Non-U.S. | Pooled corporate obligations
Guarantor Obligations [Line Items]
Gross Par Outstanding	12,232		16,288
Ceded Par Amount	1,174		1,475
Net Par Outstanding (excluding loss mitigation bonds)	11,058		14,813
Structured Finance Non-U.S. | Residential mortgage-backed security (RMBS)
Guarantor Obligations [Line Items]
Gross Par Outstanding	1,296		1,586
Ceded Par Amount	150		162
Net Par Outstanding (excluding loss mitigation bonds)	1,146		1,424
Structured Finance Non-U.S. | Commercial mortgage-backed securities (CMBS) and other commercial real estate related exposures
Guarantor Obligations [Line Items]
Gross Par Outstanding	0		100
Ceded Par Amount	0		0
Net Par Outstanding (excluding loss mitigation bonds)	0		100
Structured Finance Non-U.S. | Commercial receivables
Guarantor Obligations [Line Items]
Gross Par Outstanding	1,286		1,489
Ceded Par Amount	23		26
Net Par Outstanding (excluding loss mitigation bonds)	1,263		1,463
Structured Finance Non-U.S. | Structured credit
Guarantor Obligations [Line Items]
Gross Par Outstanding	197		669
Ceded Par Amount	21		78
Net Par Outstanding (excluding loss mitigation bonds)	176		591
Structured Finance
Guarantor Obligations [Line Items]
Gross Par Outstanding	78,005		99,723
Ceded Par Amount	5,077		6,420
Net Par Outstanding (excluding loss mitigation bonds)	$ 72,928		$ 93,303

[1] Includes $3,172 million in ceded par outstanding related to insured credit derivatives.

[2] In the third quarter of 2013, the Company adjusted its approach to assigning internal ratings. See "Refinement of Approach to Internal Credit Ratings and Surveillance Categories" above. This approach is reflected in the "Financial Guaranty Portfolio by Internal Rating" tables as of both December 31, 2013 and December 31, 2012.