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) (Detail) (USD $) In Billions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Insurance in Force	$ 679.1		$ 840.1
% of Insurance in Force	100.00%		100.00%
United States [Member]
Insurance in Force	604.3		752.5
% of Insurance in Force	89.00%		89.60%
Non-United States [Member]
Insurance in Force	74.8		87.6
% of Insurance in Force	11.00%		10.40%
Global Public Finance [Member]
Insurance in Force	580.5		707.2
% of Insurance in Force	85.50%		84.20%
Global Public Finance [Member] | United States [Member]
Insurance in Force	530.9		656.6
% of Insurance in Force	78.20%		78.20%
Global Public Finance [Member] | Non-United States [Member]
Insurance in Force	49.6		50.6
% of Insurance in Force	7.30%		6.00%
Global Structured Finance [Member]
Insurance in Force	98.6		132.9
% of Insurance in Force	14.50%		15.80%
General Obligation [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	187.5		234.3
% of Insurance in Force	27.60%		27.90%
General Obligation - Lease [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	41.7		51.7
% of Insurance in Force	6.10%		6.20%
Municipal Utilities [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	97.1		117.0
% of Insurance in Force	14.30%		13.90%
Tax-Backed [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	71.9		86.3
% of Insurance in Force	10.60%		10.30%
Tax-Backed [Member] | Global Public Finance [Member] | Non-United States [Member]
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	52.1		68.3
% of Insurance in Force	7.70%		8.10%
Transportation [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance in Force	14.2		15.0
% of Insurance in Force	2.10%		1.80%
Higher Education [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	30.3		36.9
% of Insurance in Force	4.50%		4.40%
Health Care [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	12.1		16.9
% of Insurance in Force	1.80%		2.00%
Health Care [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance in Force	0.1		0.1
% of Insurance in Force	0.00%		0.00%
Military Housing [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	19.0		19.4
% of Insurance in Force	2.80%		2.30%
Investor-Owned Utilities [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	8.7	[1]	11.5	[1]
% of Insurance in Force	1.30%	[1]	1.40%	[1]
Municipal Housing [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	7.2		9.4
% of Insurance in Force	1.00%		1.10%
Student Loans [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	0.7		2.1
% of Insurance in Force	0.10%		0.30%
Other Public Finance [Member] | Global Public Finance [Member] | United States [Member]
Insurance in Force	2.6	[2]	2.8	[2]
% of Insurance in Force	0.40%	[2]	0.30%	[2]
International Utilities [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance in Force	16.2		16.2
% of Insurance in Force	2.40%		1.90%
Sovereign Related And Sub-Sovereign [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance in Force	18.4	[3]	18.6	[3]
% of Insurance in Force	2.70%	[3]	2.20%	[3]
Local Governments [Member] | Global Public Finance [Member] | Non-United States [Member]
Insurance in Force	0.5	[4]	0.5	[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	57.6	[5]	78.7	[5]
% of Insurance in Force	8.50%	[5]	9.40%	[5]
Residential Mortgage-Backed Securities [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force	17.1		21.1
% of Insurance in Force	2.50%		2.50%
Commercial Mortgage-Backed [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force	3.8		4.4
% of Insurance in Force	0.60%		0.50%
Consumer Asset-Backed, Auto Loans [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force			0.7
% of Insurance in Force	0.00%		0.10%
Consumer Asset-Backed, Student Loans [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force	1.2		1.7
% of Insurance in Force	0.20%		0.20%
Consumer Asset-Backed, Manufactured Housing [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force	2.0		2.2
% of Insurance in Force	0.30%		0.30%
Other Consumer Asset-Backed [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force	0.1		0.2
% 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	2.5		3.2
% of Insurance in Force	0.40%		0.40%
Corporate Asset-Backed, Secured Airline Equipment Securitization (EETC) [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force	2.4		3.2
% 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	0.5		0.7
% 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	6.1		7.5
% of Insurance in Force	0.90%		0.90%
Corporate Asset-Backed, Franchise Assets [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force	0.9		1.3
% of Insurance in Force	0.10%		0.20%
Corporate Asset-Backed, Intellectual Property [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force			1.9
% of Insurance in Force	0.00%		0.20%
Corporate Asset-Backed, Future Flow [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force	0.2		0.4
% of Insurance in Force	0.00%		0.00%
Other Corporate Asset-Backed [Member] | Global Structured Finance [Member] | United States [Member]
Insurance in Force	$ 4.2		$ 5.7
% of Insurance in Force	0.60%		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.

[5] Includes transactions (represented by structured pools of primarily investment grade corporate credit risks or CRE assets) that do not include typical CDO structuring characteristics, such as tranched credit risk, cash flow waterfalls, or interest and over-collateralization coverage tests.