Outstanding Exposure - BIG Net Par Outstanding (Details) $ in Millions		1 Months Ended
		Aug. 03, 2016 USD ($)	Jul. 01, 2016 risk	Jun. 30, 2016 USD ($) risk		Dec. 31, 2015 USD ($) risk
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Credit Derivative				$ 20,014		$ 25,594
Net par amount outstanding				329,864	[1]	358,571	[2]
BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[3]			13,704		13,574
Net Par Outstanding, Credit Derivative				1,086		1,609
Net par amount outstanding				$ 14,790		$ 15,183
Number of Risks, Financial Guaranty Insurance | risk	[3],[4],[5]			405		419
Number of Risks, Credit Derivative | risk	[4]			27		32
Number of Risks | risk	[4]			432		451
BIG [Member] | BIG 1 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[3]			$ 6,546	[6]	$ 7,019
Net Par Outstanding, Credit Derivative				510	[6]	1,004
Net par amount outstanding				$ 7,056	[6]	$ 8,023
Number of Risks, Financial Guaranty Insurance | risk	[3],[4]			198	[6]	202
Number of Risks, Credit Derivative | risk	[4]			10	[6]	12
Number of Risks | risk	[4]			208	[6]	214
BIG [Member] | BIG 2 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[3]			$ 4,119		$ 3,655
Net Par Outstanding, Credit Derivative				450		474
Net par amount outstanding				$ 4,569		$ 4,129
Number of Risks, Financial Guaranty Insurance | risk	[3],[4]			76		85
Number of Risks, Credit Derivative | risk	[4]			5		8
Number of Risks | risk	[4]			81		93
BIG [Member] | BIG 3 [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, Financial Guaranty Insurance	[3]			$ 3,039	[6]	$ 2,900
Net Par Outstanding, Credit Derivative				126	[6]	131
Net par amount outstanding				$ 3,165	[6]	$ 3,031
Number of Risks, Financial Guaranty Insurance | risk	[3],[4]			131	[6]	132
Number of Risks, Credit Derivative | risk	[4]			12	[6]	12
Number of Risks | risk	[4]			143	[6]	144
Subsequent Event [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding downgraded		$ 1,803
Number of risks downgraded | risk			2

[1] Excludes $1.4 billion of loss mitigation securities insured and held by the Company as of June 30, 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

[6] Subsequent to June 30, 2016, and as a result of its July 1, 2016 Puerto Rico claim payments, the Company downgraded from BIG 1 to BIG 3 $1,803 million net par outstanding of financial guaranty insurance across two risks.