Loss And Loss Adjustment Expense Reserves (Schedule Of Financial Guarantees And Related Claim Liability) (Detail) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2016 USD ($) issue policy	Dec. 31, 2015 USD ($) issue policy
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		409	411
Number of issues | issue	[1]	141	140
Remaining weighted average contract period (in years)		7 years 6 months	7 years 4 months 24 days
Principal	[2]	$ 10,948	$ 11,160
Interest	[2]	6,085	6,247
Total	[2]	17,033	17,407
Gross claim liability		762	797
Less: Gross potential recoveries		541	752
Discount, net	[3]	109	116
Net claim liability (recoverable)		112	(71)
Unearned premium revenue		$ 97	$ 98
Caution List Low [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		55	57
Number of issues | issue	[1]	12	12
Remaining weighted average contract period (in years)		8 years 1 month 6 days	7 years 7 months 6 days
Principal	[2]	$ 2,529	$ 2,591
Interest	[2]	2,713	2,733
Total	[2]	5,242	5,324
Gross claim liability			0
Less: Gross potential recoveries			0
Discount, net	[3]		0
Net claim liability (recoverable)			0
Unearned premium revenue		$ 8	$ 8
Caution List Medium [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		16	18
Number of issues | issue	[1]	5	6
Remaining weighted average contract period (in years)		6 years 6 months	6 years 8 months 12 days
Principal	[2]	$ 147	$ 147
Interest	[2]	55	57
Total	[2]	202	204
Gross claim liability			0
Less: Gross potential recoveries			0
Discount, net	[3]		0
Net claim liability (recoverable)			0
Unearned premium revenue		$ 2	$ 2
Caution List High [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		5	171
Number of issues | issue	[1]	3	5
Remaining weighted average contract period (in years)		7 years 7 months 6 days	9 years 7 months 6 days
Principal	[2]	$ 370	$ 1,996
Interest	[2]	132	1,038
Total	[2]	502	3,034
Gross claim liability			0
Less: Gross potential recoveries			0
Discount, net	[3]		0
Net claim liability (recoverable)			0
Unearned premium revenue		$ 9	$ 33
Classified List [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		333	165
Number of issues | issue	[1]	121	117
Remaining weighted average contract period (in years)		7 years 3 months 18 days	6 years 8 months 12 days
Principal	[2]	$ 7,902	$ 6,426
Interest	[2]	3,185	2,419
Total	[2]	11,087	8,845
Gross claim liability		762	797
Less: Gross potential recoveries		541	752
Discount, net	[3]	109	116
Net claim liability (recoverable)		112	(71)
Unearned premium revenue		$ 78	$ 55

[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.