Loss And Loss Adjustment Expense Reserves (Schedule Of Financial Guarantees And Related Claim Liability) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 policy issue		Dec. 31, 2012 issue policy
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	299		295
Number of issues	180	[1]	190	[1]
Remaining weighted average contract period (in years)	9 years 8 months 12 days		8 years 8 months 12 days
Principal	$ 14,264	[2]	$ 15,257	[2]
Interest	8,632	[2]	8,361	[2]
Total	22,896	[2]	23,618	[2]
Gross claim liability	1,235		1,589
Less: Gross potential recoveries	1,085		4,109
Discount, net	205		229
Net claim liability (recoverable)	(55)		(2,749)
Unearned premium revenue	227		278
Caution List Low [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	83		54
Number of issues	26	[1]	29	[1]
Remaining weighted average contract period (in years)	11 years 0 months 0 days		8 years 1 month 6 days
Principal	5,290	[2]	4,250	[2]
Interest	3,829	[2]	2,721	[2]
Total	9,119	[2]	6,971	[2]
Gross claim liability	0		0
Less: Gross potential recoveries	0		0
Discount, net	0		0
Net claim liability (recoverable)	0		0
Unearned premium revenue	112		142
Caution List Medium [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	19		25
Number of issues	14	[1]	15	[1]
Remaining weighted average contract period (in years)	4 years 10 months 24 days		4 years 0 months 0 days
Principal	1,073	[2]	1,176	[2]
Interest	253	[2]	256	[2]
Total	1,326	[2]	1,432	[2]
Gross claim liability	0		0
Less: Gross potential recoveries	0		0
Discount, net	0		0
Net claim liability (recoverable)	0		0
Unearned premium revenue	19		11
Caution List High [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	5		10
Number of issues	4	[1]	10	[1]
Remaining weighted average contract period (in years)	11 years 6 months 0 days		7 years 7 months 6 days
Principal	40	[2]	373	[2]
Interest	24	[2]	120	[2]
Total	64	[2]	493	[2]
Gross claim liability	0		0
Less: Gross potential recoveries	0		0
Discount, net	0		0
Net claim liability (recoverable)	0		0
Unearned premium revenue	0		3
Classified List [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	192		206
Number of issues	136	[1]	136	[1]
Remaining weighted average contract period (in years)	9 years 6 months 0 days		9 years 6 months 0 days
Principal	7,861	[2]	9,458	[2]
Interest	4,526	[2]	5,264	[2]
Total	12,387	[2]	14,722	[2]
Gross claim liability	1,235		1,589
Less: Gross potential recoveries	1,085		4,109
Discount, net	205		229
Net claim liability (recoverable)	(55)		(2,749)
Unearned premium revenue	$ 96		$ 122

[1] An “issue” represents the aggregate of financial guarantee policies that share the same revenue source for purposes of making debt service payments.

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