Outstanding Exposure - BIG Net Par Outstanding (Details) $ in Millions		Sep. 30, 2015 USD ($) risk		Dec. 31, 2014 USD ($) risk
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Credit Derivative		$ 29,633	[1]	$ 34,996
Net par amount outstanding		372,361	[2],[3]	403,729	[4]
BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance		15,582		15,222
Net Par Outstanding, Credit Derivative	[5]	2,029		3,025
Net par amount outstanding		$ 17,611		$ 18,247
Number of Risks, Financial Guaranty Insurance | risk	[6]	451		358
Number of Risks, Credit Derivative | risk	[7]	33		56
Number of Risks | risk	[7]	484		414
BIG [Member] | BIG 1 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Credit Derivative		$ 1,247		$ 1,670
Net par amount outstanding		$ 10,799		$ 11,865
Number of Risks, Credit Derivative | risk	[7]	13		18
Number of Risks | risk	[7]	252		182
BIG [Member] | BIG 2 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Credit Derivative		$ 610		$ 554
Net par amount outstanding		$ 4,020		$ 2,689
Number of Risks, Credit Derivative | risk	[7]	8		14
Number of Risks | risk	[7]	95		89
BIG [Member] | BIG 3 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Credit Derivative		$ 172		$ 801
Net par amount outstanding		$ 2,792		$ 3,693
Number of Risks, Credit Derivative | risk	[7]	12		24
Number of Risks | risk	[7]	137		143
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[8]	$ 15,582		$ 15,222
Number of Risks, Financial Guaranty Insurance | risk	[6],[7],[8]	451		358
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | BIG [Member] | BIG 1 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[8]	$ 9,552		$ 10,195
Number of Risks, Financial Guaranty Insurance | risk	[6],[7],[8]	239		164
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | BIG [Member] | BIG 2 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[8]	$ 3,410		$ 2,135
Number of Risks, Financial Guaranty Insurance | risk	[6],[7],[8]	87		75
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | BIG [Member] | BIG 3 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[8]	$ 2,620		$ 2,892
Number of Risks, Financial Guaranty Insurance | risk	[6],[7],[8]	125		119

[1] The September 30, 2015 total amount includes $4.3 billion net par outstanding of credit derivatives acquired from Radian Asset.

[2] Excludes $1.6 billion of loss mitigation securities insured and held by the Company as of September 30, 2015, which are primarily BIG.

[3] The September 30, 2015 amounts include $12.4 billion of net par acquired from Radian Asset.

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

[5] The September 30, 2015 BIG amount includes $489 million net par outstanding of credit derivatives acquired from Radian Asset.

[6] 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

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

[8] Includes net par outstanding for VIEs.