Outstanding Exposure - Net Direct Economic Exposure to Selected European Countries (Details) $ in Millions	Dec. 31, 2016 USD ($)	[1]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	$ 2,249
BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	701
Hungary [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	350
Hungary [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	283
Italy [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	1,279
Italy [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	0
Portugal [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	76
Portugal [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	76
Spain [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	342
Spain [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	342
Turkey [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	202
Turkey [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	0
Sovereign and Sub Sovereign [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	1,534	[2]
Sovereign and Sub Sovereign [Member] | Hungary [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	236	[2]
Sovereign and Sub Sovereign [Member] | Italy [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	880	[2]
Sovereign and Sub Sovereign [Member] | Portugal [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	76	[2]
Sovereign and Sub Sovereign [Member] | Spain [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	342	[2]
Sovereign and Sub Sovereign [Member] | Turkey [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	0	[2]
Non-sovereign Exposure [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	715	[3]
Non-sovereign Exposure [Member] | Hungary [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	114	[3]
Non-sovereign Exposure [Member] | Italy [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	399	[3]
Non-sovereign Exposure [Member] | Portugal [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	0	[3]
Non-sovereign Exposure [Member] | Spain [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	0	[3]
Non-sovereign Exposure [Member] | Turkey [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	$ 202	[3]

[1] While exposures are shown in U.S. dollars, the obligations are in various currencies, primarily euros.

[2] Sub-sovereign exposure in Selected European Countries includes transactions backed by receivables from, or supported by, sub-sovereigns, which are governmental or government-backed entities other than the ultimate governing body of the country.

[3] (3)Non-sovereign exposure in Selected European Countries includes debt of regulated utilities, RMBS and diversified payment rights (DPR) securitizations.