Business Developments, Risks And Uncertainties, And Liquidity (Narrative) (Detail) (USD $)	3 Months Ended	6 Months Ended		12 Months Ended					6 Months Ended	57 Months Ended		6 Months Ended	12 Months Ended				6 Months Ended									6 Months Ended	12 Months Ended	6 Months Ended	57 Months Ended										6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2012 MBIA Inc. [Member]	Dec. 31, 2011 MBIA Inc. [Member]	Jun. 30, 2012 MBIA Inc General Corporate Purposes [Member]	Dec. 31, 2011 MBIA Inc General Corporate Purposes [Member]	Jun. 30, 2012 MBIA Corp [Member]	Jun. 30, 2012 MBIA Corp [Member]	Dec. 31, 2011 MBIA Corp [Member]	Jun. 30, 2012 National [Member]	Dec. 31, 2011 National [Member]	Dec. 31, 2010 National [Member]	Jun. 30, 2012 MBIA Inc Total [Member]	Dec. 31, 2011 MBIA Inc Total [Member]	Jun. 30, 2012 Maximum Amount [Member]	Jun. 30, 2012 Utilized Amount [Member] MBIA Inc. [Member]	Jun. 30, 2012 Asset Swap [Member] MBIA Inc. [Member]	Jun. 30, 2012 Asset/Liability Products [Member]	Dec. 31, 2011 Asset/Liability Products [Member]	Jun. 30, 2012 Asset/Liability Products [Member] MBIA Inc. [Member]	Dec. 31, 2011 Asset/Liability Products [Member] MBIA Inc. [Member]	Jun. 30, 2012 Fair Value Of Collateral Pledged By National [Member] Asset Swap [Member]	Jun. 30, 2012 Notional Amount Utilized [Member]	Jun. 30, 2012 Net Average Interest Rate [Member]	Jun. 30, 2011 Net Average Interest Rate [Member]	Jun. 30, 2012 Fair Value Of The Collateral Pledged By MBIA Inc [Member]	Jun. 30, 2012 Consolidated VIEs [Member] MBIA Corp [Member]	Jun. 30, 2012 Second-Lien RMBS Securitizations [Member]	Dec. 31, 2011 Maximum Amount At Inception [Member]	Jun. 30, 2012 Maximum Amount At Inception [Member] MBIA Corp [Member]	Jun. 30, 2012 CMBS Pool Insured Gross Par [Member]	Jun. 30, 2012 CRE CDO [Member]	Jun. 30, 2012 CRE Loan Pools [Member]	Jun. 30, 2012 CMBS Pool And CRE CDO Gross Par Exposure Decrease Since 2007 [Member]	Jun. 30, 2012 ABS CDO [Member]	Jun. 30, 2012 ABS CDO Gross Par Exposure Decrease Since 2007 [Member]	Jun. 30, 2012 Interest Rate [Member] MBIA Corp [Member]	Jun. 30, 2012 Borrowing Limit [Member]
Business Acquisition [Line Items]
Liquid asset					$ 336,000,000	$ 386,000,000	$ 290,000,000	$ 226,000,000	$ 534,000,000	$ 534,000,000	$ 534,000,000	$ 352,000,000	$ 703,000,000		$ 336,000,000	$ 386,000,000				$ 46,000,000	$ 160,000,000	$ 46,000,000	$ 160,000,000
Claims payments									834,000,000
Commuted gross insured exposure									12,800,000,000
Percentage of recognized estimated recoveries in relationship to consolidated total shareholders equity	83.00%	83.00%		119.00%
Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Percentage of ineligible mortgage loan recoveries of statutory capital	125.00%	125.00%		89.00%
Estimated insurance recoveries, after income taxes	2,100,000,000	2,100,000,000		2,000,000,000
Insurance par exposure	32,900,000,000	32,900,000,000																															15,700,000,000	2,500,000,000	2,900,000,000	35,900,000,000	4,600,000,000	32,700,000,000
Shareholders equity	2,503,000,000	2,503,000,000		1,700,000,000
Statutory capital									1,700,000,000	1,700,000,000		3,000,000,000
Contingency reserve release to surplus	196,000,000	196,000,000
MBIA Secured Loan, average interest rate												7.00%																											2.51%
MBIA Corp Secured Loan												1,600,000,000																				2,000,000,000
Additional borrowing under national secured loan												443,000,000
Fair value of collateral pledged																			659,000,000					642,000,000
National asset swap					2,000,000,000																				620,000,000
National asset swap, percentage																										0.39%	0.44%
Secured loan balance																															2,000,000,000
Approved secured loan maximum outstanding amount	450,000,000	450,000,000																																						450,000,000
Conduit Repurchase Agreement																	1,000,000,000	53,000,000										64,000,000
Conduit Repurchase Agreement, percentage																										2.50%
Payment on tax agreement related to estimated taxes		44,000,000											11,000,000	1,000,000
Escrow through tax years	314,000,000	314,000,000
Invested assets at amortized cost to liabilities at amortized cost issued to third-parties and affiliates at amortized cost	802,000,000	802,000,000		591,000,000
Cash payments for second lien RMBS securitizations and CDS contracts										11,500,000,000																			836,000,000
Cash payments for second lien RMBS securitization																														6,500,000,000
Ineligible mortgage loans from securitizations, related expected recoveries									3,200,000,000
Held cash and available-for-sale investments									1,500,000,000	1,500,000,000	1,500,000,000
Cash and Short-term investments												$ 421,000,000	$ 771,000,000