Insurance In Force (Schedule Of Insurance In Force By Type Of Bond, Excluding Transactions Guaranteed By MBIA Corp. On Behalf Of Various Investment Management Services Affiliated Companies) (Details) (USD $) In Billions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Insurance In Force [Line Items]
Insurance in Force	$ 840.1		$ 1,025.0
% of Insurance in Force	100.00%		100.00%
United States [Member]
Insurance In Force [Line Items]
Insurance in Force	752.5		919.1
% of Insurance in Force	89.60%		89.70%
Non-United States [Member]
Insurance In Force [Line Items]
Insurance in Force	87.6		105.9
% of Insurance in Force	10.40%		10.30%
Global Public Finance [Member]
Insurance In Force [Line Items]
Insurance in Force	707.2		833.0
% of Insurance in Force	84.20%		81.30%
Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	656.6		777.4
% of Insurance in Force	78.20%		75.80%
Global Public Finance [Member] | Non-United States [Member]
Insurance In Force [Line Items]
Insurance in Force	50.6		55.6
% of Insurance in Force	6.00%		5.50%
Global Structured Finance [Member]
Insurance In Force [Line Items]
Insurance in Force	132.9		192.0
% of Insurance in Force	15.80%		18.70%
General Obligation [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	234.3		278.7
% of Insurance in Force	27.90%		27.20%
General Obligation - Lease [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	51.7		60.2
% of Insurance in Force	6.20%		5.90%
Municipal Utilities [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	117.0		138.8
% of Insurance in Force	13.90%		13.50%
Tax-Backed [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	86.3		98.9
% of Insurance in Force	10.30%		9.60%
Tax-Backed [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance In Force [Line Items]
Insurance in Force	0.2		0.2
% of Insurance in Force	0.00%		0.00%
Transportation [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	68.3		84.5
% of Insurance in Force	8.10%		8.20%
Transportation [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance In Force [Line Items]
Insurance in Force	15.0		15.9
% of Insurance in Force	1.80%		1.60%
Higher Education [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	36.9		42.5
% of Insurance in Force	4.40%		4.10%
Health Care [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	16.9		21.4
% of Insurance in Force	2.00%		2.10%
Health Care [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance In Force [Line Items]
Insurance in Force	0.1		0
% of Insurance in Force	0.00%		0.00%
Military Housing [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	19.4		20.5
% of Insurance in Force	2.30%		2.00%
Investor-Owned Utilities [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	11.5	[1]	13.5	[1]
% of Insurance in Force	1.40%	[1]	1.30%	[1]
Municipal Housing [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	9.4		11.0
% of Insurance in Force	1.10%		1.10%
Student Loans [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	2.1		3.6
% of Insurance in Force	0.30%		0.40%
Other Public Finance [Member] | Global Public Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	2.8	[2]	3.8	[2]
% of Insurance in Force	0.30%	[2]	0.40%	[2]
International Utilities [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance In Force [Line Items]
Insurance in Force	16.2		18.6
% of Insurance in Force	1.90%		1.80%
Sovereign Related And Sub-Sovereign [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance In Force [Line Items]
Insurance in Force	18.6	[3]	20.3	[3]
% of Insurance in Force	2.20%	[3]	2.00%	[3]
Local Governments [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance In Force [Line Items]
Insurance in Force	0.5	[4]	0.6	[4]
% of Insurance in Force	0.10%	[4]	0.10%	[4]
Collateralized Debt Obligations [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	78.7		123.5
% of Insurance in Force	9.40%		12.10%
Residential Mortgage-Backed Securities [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	21.1		24.1
% of Insurance in Force	2.50%		2.40%
Commercial Mortgage Backed [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	4.4		5.4
% of Insurance in Force	0.50%		0.50%
Consumer Asset-Backed, Auto Loans [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	0.7		2.2
% of Insurance in Force	0.10%		0.20%
Consumer Asset-Backed, Student Loans [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	1.7		1.9
% of Insurance in Force	0.20%		0.20%
Consumer Asset-Backed, Manufactured Housing [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	2.2		2.5
% of Insurance in Force	0.30%		0.20%
Other Consumer Asset-Backed [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	0.2		0.4
% of Insurance in Force	0.00%		0.00%
Corporate Asset-Backed, Aircraft Portfolio Lease Securitizations [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	3.2		4.5
% of Insurance in Force	0.40%		0.40%
Corporate Asset-Backed, Rental Car Fleets [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force			0.3
% of Insurance in Force	0.00%		0.00%
Corporate Asset-Backed, Secured Airline Equipment Securitization (EETC) [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	3.2		3.5
% of Insurance in Force	0.30%		0.30%
Corporate Asset-Backed, Other Operating Assets [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	0.7		0.9
% of Insurance in Force	0.10%		0.10%
Corporate Asset-Backed, Structured Insurance Securitizations [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	7.5		9.2
% of Insurance in Force	0.90%		0.90%
Corporate Asset-Backed, Franchise Assets [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	1.3		1.6
% of Insurance in Force	0.20%		0.20%
Corporate Asset-Backed, Intellectual Property [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	1.9		3.7
% of Insurance in Force	0.20%		0.40%
Corporate Asset-Backed, Future Flow [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	0.4		1.2
% of Insurance in Force	0.00%		0.10%
Other Corporate Asset-Backed [Member] | Global Structured Finance [Member] | United States [Member]
Insurance In Force [Line Items]
Insurance in Force	$ 5.7		$ 7.1
% of Insurance in Force	0.70%		0.70%

[1] Includes investor owned utilities, industrial development and pollution control revenue bonds.

[2] Includes certain non-profit enterprises and stadium related financing.

[3] Includes regions, departments or their equivalent in each jurisdiction as well as sovereign owned entities that are supported by a sovereign state, region or department.

[4] Includes municipal owned entities backed by sponsoring local government.