Outstanding Exposure - BIG Net Par Outstanding (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014 risk		Dec. 31, 2013
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Credit Derivative	$ 34,996		$ 54,482
Net Par Outstanding (excluding loss mitigation bonds)	403,729	[1]	459,107	[2]
Number of Risks	13,161
BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	15,222	[3]	17,745	[3]
Net Par Outstanding, Credit Derivative	3,025		4,793
Net Par Outstanding (excluding loss mitigation bonds)	18,247		22,538
Number of Risks, Financial Guaranty Insurance	358	[3],[4]	384	[3],[4]
Number of Risks, Credit Derivative	56	[4]	73	[4]
Number of Risks	414	[4]	457	[4]
BIG [Member] | BIG 1 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	10,195	[3]	12,391	[3]
Net Par Outstanding, Credit Derivative	1,670		2,360
Net Par Outstanding (excluding loss mitigation bonds)	11,865		14,751
Number of Risks, Financial Guaranty Insurance	164	[3],[4]	185	[3],[4]
Number of Risks, Credit Derivative	18	[4]	25	[4]
Number of Risks	182	[4]	210	[4]
BIG [Member] | BIG 2 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	2,135	[3]	2,323	[3]
Net Par Outstanding, Credit Derivative	554		1,626
Net Par Outstanding (excluding loss mitigation bonds)	2,689		3,949
Number of Risks, Financial Guaranty Insurance	75	[3],[4]	80	[3],[4]
Number of Risks, Credit Derivative	14	[4]	21	[4]
Number of Risks	89	[4]	101	[4]
BIG [Member] | BIG 3 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	2,892	[3]	3,031	[3]
Net Par Outstanding, Credit Derivative	801		807
Net Par Outstanding (excluding loss mitigation bonds)	$ 3,693		$ 3,838
Number of Risks, Financial Guaranty Insurance	119	[3],[4]	119	[3],[4]
Number of Risks, Credit Derivative	24	[4]	27	[4]
Number of Risks	143	[4]	146	[4]

[1] Excludes $1.3 billion of loss mitigation securities insured and held by the Company as of December 31, 2014, which are primarily in the BIG category.

[2] Excludes $1.2 billion of loss mitigation securities insured and held by the Company as of December 31, 2013, which are primarily in the BIG category.

[3] Includes net par outstanding for FG VIEs.

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