Outstanding Exposure - Puerto Rico Gross Par and Gross Debt Service Outstanding (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Schedule of Insured Financial Obligations [Line Items]
Gross Par Outstanding		$ 373,192	$ 426,704
Gross Debt Service Outstanding		559,470	646,722
Puerto Rico [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Par Outstanding		5,755	6,035
Gross Debt Service Outstanding		9,632	10,074
Subject to the Terms of the Recovery Act [Member] | Puerto Rico [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Par Outstanding	[1]	2,965	3,058
Gross Debt Service Outstanding	[1]	5,162	5,326
Not Subject to the Terms of the Recovery Act [Member] | Puerto Rico [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Par Outstanding		2,790	2,977
Gross Debt Service Outstanding		$ 4,470	$ 4,748

[1] On February 6, 2015, the U.S. District Court for the District of Puerto Rico ruled that the Recovery Act is preempted by the U.S. Bankruptcy Code and is therefore void. On July 6, 2015, the U.S. Court of Appeals for the First Circuit upheld that ruling, and on December 4, 2015, the U.S. Supreme Court granted petitions for writs of certiorari relating to that ruling.