Outstanding Exposure - Puerto Rico Net Par Outstanding (Details) - USD ($) $ in Millions	Jun. 30, 2015		Dec. 31, 2014
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	$ 390,384	[1],[2]	$ 403,729	[3]
Puerto Rico [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	5,430	[4],[5]	4,939
Puerto Rico [Member] | Subject to the Terms of the Recovery Act [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	2,705	[4],[5]	2,447
Puerto Rico [Member] | Subject to the Terms of the Recovery Act [Member] | PRHTA (Transportation revenue) [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	934	[4],[5]	844
Puerto Rico [Member] | Subject to the Terms of the Recovery Act [Member] | PREPA [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	818	[4],[5]	772
Puerto Rico [Member] | Subject to the Terms of the Recovery Act [Member] | Puerto Rico Aqueduct and Sewer Authority [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	403	[4],[5]	384
Puerto Rico [Member] | Subject to the Terms of the Recovery Act [Member] | PRHTA (Highway revenue) [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	376	[4],[5]	273
Puerto Rico [Member] | Subject to the Terms of the Recovery Act [Member] | Puerto Rico Convention Center District Authority [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	174	[4],[5]	174
Puerto Rico [Member] | Not Subject to the Terms of the Recovery Act [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	2,725	[4],[5]	2,492
Puerto Rico [Member] | Not Subject to the Terms of the Recovery Act [Member] | Commonwealth of Puerto Rico - General Obligation Bonds [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	1,744	[4],[5]	1,672
Puerto Rico [Member] | Not Subject to the Terms of the Recovery Act [Member] | Puerto Rico Municipal Finance Agency [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	444	[4],[5]	399
Puerto Rico [Member] | Not Subject to the Terms of the Recovery Act [Member] | Puerto Rico Sales Tax Financing Corporation [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	269	[4],[5]	269
Puerto Rico [Member] | Not Subject to the Terms of the Recovery Act [Member] | Puerto Rico Public Buildings Authority [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	216	[4],[5]	100
Puerto Rico [Member] | Not Subject to the Terms of the Recovery Act [Member] | GDB [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	33	[4],[5]	33
Puerto Rico [Member] | Not Subject to the Terms of the Recovery Act [Member] | PRIFA [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	18	[4],[5]	18
Puerto Rico [Member] | Not Subject to the Terms of the Recovery Act [Member] | University of Puerto Rico [Member]
Schedule of Insured Financial Obligations [Line Items]
Net par amount outstanding	$ 1	[4],[5]	$ 1

[1] Excludes $1.2 billion of loss mitigation securities insured and held by the Company as of June 30, 2015, which are primarily in the BIG category.

[2] amounts include $13.1 billion of net par acquired from Radian Asset.

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

[4] In July 2015, various Puerto Rico issuers made payment on $293 million of par scheduled to be paid; of that amount, $74 million and $31 million of par was paid by PREPA and PRHTA, respectively.

[5] In Second Quarter 2015, the Company's Puerto Rico exposures increased due to (1) the Radian Asset Acquisition, which increased net par outstanding by $422 million, of which $22 million was for PREPA and $169 million for PRHTA, and (2) a commutation of previously ceded Puerto Rico exposures.