Outstanding Exposure (Details 5) (USD $) In Millions, unless otherwise specified			9 Months Ended										1 Months Ended							9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 PUERTO RICO	Sep. 30, 2013 PUERTO RICO Sovereign Debt [Member]	Sep. 30, 2013 PUERTO RICO Structured finance	Sep. 30, 2013 PUERTO RICO Internal Credit, BBB- Rating [Member] Commonwealth of Puerto Rico [Member]	Sep. 30, 2013 PUERTO RICO Internal Credit, BBB- Rating [Member] Puerto Rico Highways and Transportation Authority, Transportation Revenue [Member]	Sep. 30, 2013 PUERTO RICO Internal Credit, BBB- Rating [Member] Puerto Rico Municipal Finance Authority [Member]	Sep. 30, 2013 PUERTO RICO Internal Credit, BBB- Rating [Member] Puerto Rico Public Building Authority [Member]	Sep. 30, 2013 PUERTO RICO Internal Credit, BBB- Rating [Member] Government Development Bank for Puerto Rico [Member]	Sep. 30, 2013 PUERTO RICO Internal Credit, BBB- Rating [Member] Puerto Rico Infrastructure Financing Authority [Member]	Sep. 30, 2013 PUERTO RICO Internal Credit, BBB- Rating [Member] University of Puerto Rico [Member]	Jul. 31, 2013 PUERTO RICO Internal Credit, BB plus Rating [Member] Puerto Rico Aqueduct and Sewer Authority [Member]	Sep. 30, 2013 PUERTO RICO Internal Credit, BB plus Rating [Member] Puerto Rico Aqueduct and Sewer Authority [Member]	Sep. 30, 2013 PUERTO RICO Internal Credit, BB plus Rating [Member] Puerto Rico Public Finance Corporation [Member]	Sep. 30, 2013 PUERTO RICO BBB Puerto Rico Electric Power Authority [Member]	Sep. 30, 2013 PUERTO RICO BBB Puerto Rico Highways and Transportation Authority, Highway Revenue [Member]	Sep. 30, 2013 PUERTO RICO BBB Puerto Rico Convention Center District Authority [Member]	Sep. 30, 2013 PUERTO RICO A Puerto Rico Sales Tax Financing Corporation [Member]	Sep. 30, 2013 Investment Grade [Member] PUERTO RICO	Sep. 30, 2013 Below Investment Grade [Member] PUERTO RICO
Guarantor Obligations [Line Items]
Insured Financial Obligations Outstanding Principal Amount	$ 474,667	$ 519,893	$ 5,497	$ 2,100	$ 2,900	$ 1,885	$ 928	$ 450	$ 139	$ 33	$ 18	$ 1		$ 384	$ 44	$ 860	$ 303	$ 185	$ 267
Insured Financial Obligations, External Credit Rating, Percentage																				92.00%	8.00%
Insured Financial Obligations, Increase (Decrease) in Net Par Exposure, Percentage			17.00%
Public Utilities, Approved Rate Increase (Decrease), Percentage													60.00%