Loss And Loss Adjustment Expense Reserves (Schedule Of Financial Guarantees And Related Claim Liability) (Detail) $ in Millions		3 Months Ended	12 Months Ended
		Jun. 30, 2015 USD ($) issue policy	Dec. 31, 2014 USD ($) issue policy
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		336	315
Number of issues | issue	[1]	142	147
Remaining weighted average contract period (in years)		7 years 9 months 18 days	7 years 8 months 12 days
Principal	[2]	$ 12,212	$ 11,263
Interest	[2]	6,792	4,620
Total	[2]	19,004	15,883
Gross claim liability		913	850
Less: Gross potential recoveries		966	860
Discount, net	[3]	(75)	14
Net claim liability (recoverable)		22	(24)
Unearned premium revenue		$ 153	$ 167
Caution List Low [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		58	38
Number of issues | issue	[1]	13	18
Remaining weighted average contract period (in years)		7 years 10 months 24 days	7 years 2 months 12 days
Principal	[2]	$ 3,365	$ 1,757
Interest	[2]	3,082	696
Total	[2]	6,447	2,453
Gross claim liability		0	0
Less: Gross potential recoveries		0	0
Discount, net	[3]	0	0
Net claim liability (recoverable)		0	0
Unearned premium revenue		$ 61	$ 63
Caution List Medium [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		103	98
Number of issues | issue	[1]	7	7
Remaining weighted average contract period (in years)		11 years 8 months 12 days	12 years
Principal	[2]	$ 1,421	$ 1,372
Interest	[2]	840	819
Total	[2]	2,261	2,191
Gross claim liability		0	0
Less: Gross potential recoveries		0	0
Discount, net	[3]	0	0
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 | policy		7	4
Number of issues | issue	[1]	5	3
Remaining weighted average contract period (in years)		7 years 9 months 18 days	10 years 1 month 6 days
Principal	[2]	$ 449	$ 133
Interest	[2]	166	68
Total	[2]	615	201
Gross claim liability		0	0
Less: Gross potential recoveries		0	0
Discount, net	[3]	0	0
Net claim liability (recoverable)		0	0
Unearned premium revenue		$ 11	$ 5
Classified List [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Number of policies | policy		168	175
Number of issues | issue	[1]	117	119
Remaining weighted average contract period (in years)		7 years	7 years
Principal	[2]	$ 6,977	$ 8,001
Interest	[2]	2,704	3,037
Total	[2]	9,681	11,038
Gross claim liability		913	850
Less: Gross potential recoveries		966	860
Discount, net	[3]	(75)	14
Net claim liability (recoverable)		22	(24)
Unearned premium revenue		$ 63	$ 80

[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.