Variable Interest Entities (Summary Of Maximum Exposure To Loss For Nonconsolidated VIEs) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Collateralized Debt Obligations [Member]
Investment Holdings [Line Items]
VIEs Assets	$ 27,830		$ 30,628
Maximum Exposure to Loss	15,690		18,068
Investments	61	[1]	126	[1]
Premiums Receivable	66	[2]	78	[2]
Unearned Premium Revenue	57	[3]	68
Derivative Liabilities	122	[4]	360	[4]
Residential Mortgage-Backed Securities [Member]
Investment Holdings [Line Items]
VIEs Assets	49,725		56,828
Maximum Exposure to Loss	16,537		18,494
Investments	63	[1]	71	[1]
Premiums Receivable	88	[2]	95	[2]
Insurance Loss Recoverable	2,505	[5]	2,270	[5]
Unearned Premium Revenue	87	[3]	93
Loss and Loss Adjustment Expense Reserves	469	[6]	598	[6]
Derivative Liabilities	4	[4]	3	[4]
Commercial Mortgage-Backed [Member]
Investment Holdings [Line Items]
VIEs Assets	5,293		5,547
Maximum Exposure to Loss	2,906		3,138
Premiums Receivable	2	[2]	2	[2]
Unearned Premium Revenue	2	[3]	2
Consumer Asset-Backed [Member]
Investment Holdings [Line Items]
VIEs Assets	8,396		11,709
Maximum Exposure to Loss	4,854		6,780
Investments	17	[1]	19	[1]
Premiums Receivable	27	[2]	30	[2]
Unearned Premium Revenue	26	[3]	29
Loss and Loss Adjustment Expense Reserves	30	[6]
Corporate Asset-Backed [Member]
Investment Holdings [Line Items]
VIEs Assets	30,640		42,380
Maximum Exposure to Loss	16,235		22,468
Investments	245	[1]	246	[1]
Premiums Receivable	209	[2]	325	[2]
Insurance Loss Recoverable	27	[5]	5	[5]
Unearned Premium Revenue	224	[3]	340
Derivative Liabilities	1	[4]
Global Structured Finance [Member]
Investment Holdings [Line Items]
VIEs Assets	121,884		147,092
Maximum Exposure to Loss	56,222		68,948
Investments	386	[1]	462	[1]
Premiums Receivable	392	[2]	530	[2]
Insurance Loss Recoverable	2,532	[5]	2,275	[5]
Unearned Premium Revenue	396	[3]	532
Loss and Loss Adjustment Expense Reserves	499	[6]	598	[6]
Derivative Liabilities	127	[4]	363	[4]
Global Public Finance [Member]
Investment Holdings [Line Items]
VIEs Assets	41,272		42,370
Maximum Exposure to Loss	21,879		21,201
Premiums Receivable	211	[2]	225	[2]
Unearned Premium Revenue	265	[3]	280
Total Insurance [Member]
Investment Holdings [Line Items]
VIEs Assets	163,156		189,462
Maximum Exposure to Loss	78,101		90,149
Investments	386	[1]	462	[1]
Premiums Receivable	603	[2]	755	[2]
Insurance Loss Recoverable	2,532	[5]	2,275	[5]
Unearned Premium Revenue	661	[3]	812
Loss and Loss Adjustment Expense Reserves	499	[6]	598	[6]
Derivative Liabilities	$ 127	[4]	$ 363	[4]

[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 "Derivative liabilities" on MBIA's consolidated balance sheets.

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

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