Outstanding Exposure - BIG Net Par Outstanding (Details) $ in Millions		Mar. 31, 2016 USD ($) risk		Dec. 31, 2015 USD ($) risk
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Credit Derivative		$ 24,866		$ 25,594
Net par amount outstanding		347,015	[1]	358,571	[2]
BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[3]	13,538		13,574
Net Par Outstanding, Credit Derivative		1,579		1,609
Net par amount outstanding		$ 15,117		$ 15,183
Number of Risks, Financial Guaranty Insurance | risk	[3],[4],[5]	417		419
Number of Risks, Credit Derivative | risk	[4]	31		32
Number of Risks | risk	[4]	448		451
BIG [Member] | BIG 1 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[3]	$ 6,585		$ 7,019
Net Par Outstanding, Credit Derivative		972		1,004
Net par amount outstanding		$ 7,557		$ 8,023
Number of Risks, Financial Guaranty Insurance | risk	[3],[4]	202		202
Number of Risks, Credit Derivative | risk	[4]	12		12
Number of Risks | risk	[4]	214		214
BIG [Member] | BIG 2 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[3]	$ 4,015		$ 3,655
Net Par Outstanding, Credit Derivative		480		474
Net par amount outstanding		$ 4,495		$ 4,129
Number of Risks, Financial Guaranty Insurance | risk	[3],[4]	86		85
Number of Risks, Credit Derivative | risk	[4]	7		8
Number of Risks | risk	[4]	93		93
BIG [Member] | BIG 3 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[3]	$ 2,938		$ 2,900
Net Par Outstanding, Credit Derivative		127		131
Net par amount outstanding		$ 3,065		$ 3,031
Number of Risks, Financial Guaranty Insurance | risk	[3],[4]	129		132
Number of Risks, Credit Derivative | risk	[4]	12		12
Number of Risks | risk	[4]	141		144

[1] Excludes $1.5 billion of loss mitigation securities insured and held by the Company as of March 31, 2016, which are primarily BIG.

[2] Excludes $1.5 billion of loss mitigation securities insured and held by the Company as of December 31, 2015, which are primarily BIG.

[3] Includes net par outstanding for 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.

[5] 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