Loss And Loss Adjustment Expense Reserves (Schedule Of Financial Guarantees And Related Claim Liability) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014 policy issue		Dec. 31, 2013 issue policy
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	422		299
Number of issues	186	[1]	180	[1]
Remaining weighted average contract period (in years)	9 years 9 months 18 days		9 years 8 months 12 days
Principal	$ 16,032	[2]	$ 14,264	[2]
Interest	9,550	[2]	8,632	[2]
Total	25,582	[2]	22,896	[2]
Gross claim liability	1,166		1,235
Less: Gross potential recoveries	1,006		1,085
Discount, net	217	[3]	205	[3]
Net claim liability (recoverable)	(57)		(55)
Unearned premium revenue	244		227
Caution List Low [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	208		83
Number of issues	30	[1]	26	[1]
Remaining weighted average contract period (in years)	11 years 7 months 6 days		11 years 0 months 0 days
Principal	7,585	[2]	5,290	[2]
Interest	5,356	[2]	3,829	[2]
Total	12,941	[2]	9,119	[2]
Gross claim liability	0		0
Less: Gross potential recoveries	0		0
Discount, net	0	[3]	0	[3]
Net claim liability (recoverable)	0		0
Unearned premium revenue	137		112
Caution List Medium [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	16		19
Number of issues	12	[1]	14	[1]
Remaining weighted average contract period (in years)	4 years 7 months 6 days		4 years 10 months 24 days
Principal	1,008	[2]	1,073	[2]
Interest	229	[2]	253	[2]
Total	1,237	[2]	1,326	[2]
Gross claim liability	0		0
Less: Gross potential recoveries	0		0
Discount, net	0	[3]	0	[3]
Net claim liability (recoverable)	0		0
Unearned premium revenue	18		19
Caution List High [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	5		5
Number of issues	4	[1]	4	[1]
Remaining weighted average contract period (in years)	11 years 3 months 18 days		11 years 6 months 0 days
Principal	40	[2]	40	[2]
Interest	23	[2]	24	[2]
Total	63	[2]	64	[2]
Gross claim liability	0		0
Less: Gross potential recoveries	0		0
Discount, net	0	[3]	0	[3]
Net claim liability (recoverable)	0		0
Unearned premium revenue	0		0
Classified List [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies	193		192
Number of issues	140	[1]	136	[1]
Remaining weighted average contract period (in years)	8 years 8 months 12 days		9 years 6 months 0 days
Principal	7,399	[2]	7,861	[2]
Interest	3,942	[2]	4,526	[2]
Total	11,341	[2]	12,387	[2]
Gross claim liability	1,166		1,235
Less: Gross potential recoveries	1,006		1,085
Discount, net	217	[3]	205	[3]
Net claim liability (recoverable)	(57)		(55)
Unearned premium revenue	$ 89		$ 96

[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.

[3] Represents discount related to Gross Claim Liability and Gross Potential Recoveries.