Loss And Loss Adjustment Expense Reserves (RMBS Reserves) (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended										12 Months Ended			12 Months Ended				0 Months Ended	6 Months Ended	12 Months Ended	0 Months Ended	6 Months Ended		24 Months Ended	6 Months Ended			12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2013 Loss And Lae Reserves [Member]	Dec. 31, 2012 Loss And Lae Reserves [Member]	Dec. 31, 2011 Loss And Lae Reserves [Member]	Dec. 31, 2013 Classified [Member] Loss And Lae Reserves [Member]	Dec. 31, 2012 Classified [Member] Loss And Lae Reserves [Member]	Dec. 31, 2013 First Lien R M B S Reserves [Member]	Dec. 31, 2013 First Lien R M B S Reserves [Member] Loss And Lae Reserves [Member]	Dec. 31, 2013 First Lien R M B S Reserves [Member] Variable Interest Entity Primary Beneficiary [Member]	Dec. 31, 2013 First Lien R M B S Reserves [Member] ALT-A [Member]	Dec. 31, 2013 First Lien R M B S Reserves [Member] Foreclosure [Member]	Dec. 31, 2013 First Lien R M B S Reserves [Member] Real Estate Owned [Member]	Dec. 31, 2013 First Lien R M B S Reserves [Member] Bankruptcy [Member]	Nov. 30, 2013 Rmbs And Heloc And Ces [Member]	May 31, 2014 Rmbs And Heloc And Ces [Member]	Dec. 31, 2013 Rmbs And Heloc And Ces [Member]	Jun. 30, 2014 Rmbs And Heloc And Ces [Member] Scenario Forecast [Member]	May 31, 2014 Rmbs And Heloc And Ces [Member] Scenario Forecast [Member]	May 31, 2014 Rmbs And Heloc And Ces [Member] Scenario Forecast [Member] Minimum [Member]	Nov. 30, 2015 Rmbs And Heloc And Ces [Member] Scenario Forecast [Member] Maximum [Member]	May 31, 2014 Rmbs And Heloc And Ces [Member] Scenario Forecast [Member] Rate Reduction [Member]	Dec. 31, 2013 Rmbs And Heloc And Ces [Member] Excess Spread [Member]	Dec. 31, 2012 Rmbs And Heloc And Ces [Member] Excess Spread [Member]	Dec. 31, 2013 U S Public Finance Insurance [Member]	Dec. 31, 2013 U S Public Finance Insurance [Member] General obligations	Dec. 31, 2013 U S Public Finance Insurance [Member] General obligations Classified [Member]	Dec. 31, 2013 Second Lien R M B S Securitizations [Member] Loss And Lae Reserves [Member]	Dec. 31, 2013 Second Lien R M B S Securitizations [Member] Variable Interest Entity Primary Beneficiary [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss and loss adjustment expense reserves						$ 641	$ 853	$ 836	$ 641	$ 853		$ 241	$ 2															$ 87			$ 126	$ 43
Insurance loss recoverable																										647	780	13
Schedule Of Insured Financial Obligations With Credit Deterioration Insured Contractual Payments Outstanding Principal	14,264	[1]	15,257	[1]																									124,900	161
Policyholder Benefits And Claims Incurred Net	117		50		(80)																							105
Charged-off loans recovery values	0
Delinquency period charged off on transaction specific basis, days											90
Total excess spread recoveries																										681	906
Expected recoveries of future payments						206	332																			34	126
Assumed roll rate for loans															90.00%	90.00%	75.00%
90+ day roll rate to loss set stress scenario											90.00%
Percentage of roll to loss after declining over a 24-month period														25.00%
Assumed roll rate for ninety plus day delinquent loans excluding foreclosure and real estate owned																				95.00%
Period of elevated delinquency and loss for base case, beginning, months																			6
Percentage of loans in 30-59 days delinquent bucket																		10.00%
Percentage of loans charged-off																		30.00%
Percentage of Current Roll to Loss for the transaction																		3.00%
Decrease in percentage of Current Roll to Loss for transaction																						25.00%			0.75%
Current Roll to Loss																					0.00%
Period of elevated delinquency and loss for stress case, additional months																							6	24
Addition to case basis reserves if losses remain at peak levels																				$ 70

[1] Represents contractual principal and interest payments due by the issuer of the obligations insured by MBIA.