Outstanding Exposure - Net Direct Economic Exposure to Selected European Countries (Details) $ in Millions		Jun. 30, 2015 USD ($)
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	$ 2,269
BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	894
Hungary [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	466
Hungary [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	397
Italy [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	1,306
Italy [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	0
Portugal [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	101
Portugal [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	101
Spain [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	396
Spain [Member] | BIG [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	396
Total Sovereign Exposure [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	1,599
Total Sovereign Exposure [Member] | Non-Infrastructure Public Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1],[2]	1,160
Total Sovereign Exposure [Member] | Infrastructure finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	439
Total Sovereign Exposure [Member] | Hungary [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	291
Total Sovereign Exposure [Member] | Hungary [Member] | Non-Infrastructure Public Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1],[2]	0
Total Sovereign Exposure [Member] | Hungary [Member] | Infrastructure finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	291
Total Sovereign Exposure [Member] | Italy [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	824
Total Sovereign Exposure [Member] | Italy [Member] | Non-Infrastructure Public Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1],[2]	813
Total Sovereign Exposure [Member] | Italy [Member] | Infrastructure finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	11
Total Sovereign Exposure [Member] | Portugal [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	101
Total Sovereign Exposure [Member] | Portugal [Member] | Non-Infrastructure Public Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1],[2]	90
Total Sovereign Exposure [Member] | Portugal [Member] | Infrastructure finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	11
Total Sovereign Exposure [Member] | Spain [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	383
Total Sovereign Exposure [Member] | Spain [Member] | Non-Infrastructure Public Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1],[2]	257
Total Sovereign Exposure [Member] | Spain [Member] | Infrastructure finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure		126
Total Non-sovereign Exposure [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	670
Total Non-sovereign Exposure [Member] | Regulated utilities [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	226
Total Non-sovereign Exposure [Member] | Residential Mortgage Backed Securities And Other Structured Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	444
Total Non-sovereign Exposure [Member] | Hungary [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	175
Total Non-sovereign Exposure [Member] | Hungary [Member] | Regulated utilities [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	0
Total Non-sovereign Exposure [Member] | Hungary [Member] | Residential Mortgage Backed Securities And Other Structured Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure		175
Total Non-sovereign Exposure [Member] | Italy [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	482
Total Non-sovereign Exposure [Member] | Italy [Member] | Regulated utilities [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	226
Total Non-sovereign Exposure [Member] | Italy [Member] | Residential Mortgage Backed Securities And Other Structured Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	256
Total Non-sovereign Exposure [Member] | Portugal [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	0
Total Non-sovereign Exposure [Member] | Portugal [Member] | Regulated utilities [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	0
Total Non-sovereign Exposure [Member] | Portugal [Member] | Residential Mortgage Backed Securities And Other Structured Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	0
Total Non-sovereign Exposure [Member] | Spain [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	13
Total Non-sovereign Exposure [Member] | Spain [Member] | Regulated utilities [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure		0
Total Non-sovereign Exposure [Member] | Spain [Member] | Residential Mortgage Backed Securities And Other Structured Finance [Member]
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding, European Exposure	[1]	$ 13

[1] While the Company’s exposures are shown in U.S. dollars, the obligations the Company insures are in various currencies, primarily Euros. One of the residential mortgage-backed securities included in the table above includes residential mortgages in both Italy and Germany, and only the portion of the transaction equal to the portion of the original mortgage pool in Italian mortgages is shown in the table.

[2] The exposure shown in the “Non-infrastructure public finance” category is from transactions backed by receivable payments from sub-sovereigns in Italy, Spain and Portugal. Sub-sovereign debt is debt issued by a governmental entity or government backed entity, or supported by such an entity, that is other than direct sovereign debt of the ultimate governing body of the country.