Variable Interest Entities (Summary Of Nonconsolidated VIEs Assets And Liabilities) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Investment Holdings [Line Items]
Insurance loss recoverable	$ 3,212		$ 3,046
Collateralized Debt Obligations [Member]
Investment Holdings [Line Items]
VIE Assets	20,373		26,507
Maximum Exposure to Loss	11,539		15,466
Investments	1	[1]	42	[1]
Premiums receivable	61	[2]	67	[2]
Unearned premium revenue	54	[3]	58	[3]
Loss and loss adjustment expense reserves	2	[4]	3	[4]
Derivative liabilities	108	[5]	113	[5]
Residential Mortgage-Backed Securities [Member]
Investment Holdings [Line Items]
VIE Assets	38,287		47,669
Maximum Exposure to Loss	14,093		16,379
Investments	11	[1]	25	[1]
Premiums receivable	80	[2]	87	[2]
Insurance loss recoverable	2,925	[6]	2,773	[6]
Unearned premium revenue	79	[3]	86	[3]
Loss and loss adjustment expense reserves	408	[4]	428	[4]
Derivative liabilities	5	[5]	5	[5]
Commercial Mortgage-Backed [Member]
Investment Holdings [Line Items]
VIE Assets	4,784		5,001
Maximum Exposure to Loss	2,493		2,644
Premiums receivable	2	[2]	2	[2]
Unearned premium revenue	2	[3]	2	[3]
Consumer Asset-Backed [Member]
Investment Holdings [Line Items]
VIE Assets	6,584		8,015
Maximum Exposure to Loss	3,668		4,563
Investments	11	[1]	16	[1]
Premiums receivable	21	[2]	26	[2]
Unearned premium revenue	21	[3]	25	[3]
Loss and loss adjustment expense reserves	18	[4]	23	[4]
Corporate Asset-Backed [Member]
Investment Holdings [Line Items]
VIE Assets	24,913		29,855
Maximum Exposure to Loss	12,522		15,577
Investments			241	[1]
Premiums receivable	155	[2]	192	[2]
Insurance loss recoverable	21	[6]	22	[6]
Unearned premium revenue	168	[3]	205	[3]
Derivative liabilities	1	[5]	1	[5]
Total Global Structured Finance [Member]
Investment Holdings [Line Items]
VIE Assets	94,941		117,047
Maximum Exposure to Loss	44,315		54,629
Investments	23	[1]	324	[1]
Premiums receivable	319	[2]	374	[2]
Insurance loss recoverable	2,946	[6]	2,795	[6]
Unearned premium revenue	324	[3]	376	[3]
Loss and loss adjustment expense reserves	428	[4]	454	[4]
Derivative liabilities	114	[5]	119	[5]
Global Public Finance [Member]
Investment Holdings [Line Items]
VIE Assets	43,097		42,106
Maximum Exposure to Loss	21,195		21,774
Premiums receivable	212	[2]	215	[2]
Unearned premium revenue	265	[3]	270	[3]
Total Insurance [Member]
Investment Holdings [Line Items]
VIE Assets	138,038		159,153
Maximum Exposure to Loss	65,510		76,403
Investments	23	[1]	324	[1]
Premiums receivable	531	[2]	589	[2]
Insurance loss recoverable	2,946	[6]	2,795	[6]
Unearned premium revenue	589	[3]	646	[3]
Loss and loss adjustment expense reserves	428	[4]	454	[4]
Derivative liabilities	$ 114	[5]	$ 119	[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.