Variable Interest Entities (Summary Of Nonconsolidated VIEs Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Variable Interest Entity [Line Items]
Unearned Premium Revenue
Collateralized Debt Obligations [Member]
Variable Interest Entity [Line Items]
VIE Assets	26,507		30,628
Maximum Exposure to Loss	15,466		18,068
Total investments	42	[1]	126	[1]
Premiums Receivable	67	[2]	78
Unearned Premium Revenue	58	[3]	68	[3]
Loss and Loss Adjustment Expense Reserves	3	[4]
Derivative Liabilities	113	[5]	360	[5]
Residential Mortgage-Backed Securities [Member]
Variable Interest Entity [Line Items]
VIE Assets	47,669		56,828
Maximum Exposure to Loss	16,379		18,494
Total investments	25	[1]	71	[1]
Premiums Receivable	87	[2]	95
Insurance Loss Recoverable	2,773	[6]	2,270	[6]
Unearned Premium Revenue	86	[3]	93	[3]
Loss and Loss Adjustment Expense Reserves	428	[4]	598	[4]
Derivative Liabilities	5	[5]	3	[5]
Commercial Mortgage Backed [Member]
Variable Interest Entity [Line Items]
VIE Assets	5,001		5,547
Maximum Exposure to Loss	2,644		3,138
Premiums Receivable	2	[2]	2
Unearned Premium Revenue	2	[3]	2	[3]
Consumer Asset-Backed [Member]
Variable Interest Entity [Line Items]
VIE Assets	8,015		11,709
Maximum Exposure to Loss	4,563		6,780
Total investments	16	[1]	19	[1]
Premiums Receivable	26	[2]	30
Unearned Premium Revenue	25	[3]	29	[3]
Loss and Loss Adjustment Expense Reserves	23	[4]
Corporate Asset-Backed [Member]
Variable Interest Entity [Line Items]
VIE Assets	29,855		42,380
Maximum Exposure to Loss	15,577		22,468
Total investments	241	[1]	246	[1]
Premiums Receivable	192	[2]	325
Insurance Loss Recoverable	22	[6]	5	[6]
Unearned Premium Revenue	205	[3]	340	[3]
Derivative Liabilities	1	[5]
Global Structured Finance [Member]
Variable Interest Entity [Line Items]
VIE Assets	117,047		147,092
Maximum Exposure to Loss	54,629		68,948
Total investments	324	[1]	462	[1]
Premiums Receivable	374	[2]	530
Insurance Loss Recoverable	2,795	[6]	2,275	[6]
Unearned Premium Revenue	376	[3]	532	[3]
Loss and Loss Adjustment Expense Reserves	454	[4]	598	[4]
Derivative Liabilities	119	[5]	363	[5]
Global Public Finance [Member]
Variable Interest Entity [Line Items]
VIE Assets	42,106		42,370
Maximum Exposure to Loss	21,774		21,201
Premiums Receivable	215	[2]	225
Unearned Premium Revenue	270	[3]	280	[3]
Total Insurance [Member]
Variable Interest Entity [Line Items]
VIE Assets	159,153		189,462
Maximum Exposure to Loss	76,403		90,149
Total investments	324	[1]	462	[1]
Premiums Receivable	589	[2]	755
Insurance Loss Recoverable	2,795	[6]	2,275	[6]
Unearned Premium Revenue	646	[3]	812	[3]
Loss and Loss Adjustment Expense Reserves	454	[4]	598	[4]
Derivative Liabilities	$ 119	[5]	$ 363	[5]

[1] Reported within "Investments" on MBIA's consolidated balance sheets.

[2] Reported within "Premiums receivable" on MBIA's consolidated balance sheets.

[3] Reported within "Unearned premium revenue" on MBIA's consolidated balance sheets.

[4] Reported within "Loss and loss adjustment expense reserves" on MBIA's consolidated balance sheets.

[5] Reported within "Derivative liabilities" on MBIA's consolidated balance sheets.

[6] Reported within "Insurance loss recoverable" on MBIA's consolidated balance sheets.