Variable Interest Entities (Summary Of Nonconsolidated VIEs Assets And Liabilities) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Collateralized Debt Obligations [Member]
Variable Interest Entity [Line Items]
VIE Assets	$ 9,371		$ 12,565
Maximum Exposure to Loss	6,516		7,693
Investments	125	[1]	120	[1]
Premiums receivable	34	[2]	43	[2]
Insurance loss recoverable	0	[3]	0	[3]
Unearned premium revenue	29	[4]	37	[4]
Loss and loss adjustment expense reserves	15	[5]	21	[5]
Derivative liabilities	91	[6]	108	[6]
Residential Mortgage Backed Securities [Member]
Variable Interest Entity [Line Items]
VIE Assets	16,247		21,738
Maximum Exposure to Loss	8,537		9,251
Investments	12	[1]	10	[1]
Premiums receivable	50	[2]	53	[2]
Insurance loss recoverable	639	[3]	658	[3]
Unearned premium revenue	48	[4]	51	[4]
Loss and loss adjustment expense reserves	327	[5]	327	[5]
Derivative liabilities	5	[6]	5	[6]
Commercial Mortgage Backed Securities [Member]
Variable Interest Entity [Line Items]
VIE Assets	634		1,367
Maximum Exposure to Loss	332		447
Investments		[1]	0	[1]
Premiums receivable	1	[2]	1	[2]
Insurance loss recoverable		[3]	0	[3]
Unearned premium revenue	1	[4]	1	[4]
Loss and loss adjustment expense reserves		[5]	0	[5]
Derivative liabilities		[6]	0	[6]
Consumer Asset Backed [Member]
Variable Interest Entity [Line Items]
VIE Assets	5,486		7,830
Maximum Exposure to Loss	2,513		2,740
Investments		[1]	9	[1]
Premiums receivable	18	[2]	19	[2]
Insurance loss recoverable		[3]	0	[3]
Unearned premium revenue	17	[4]	19	[4]
Loss and loss adjustment expense reserves	11	[5]	13	[5]
Derivative liabilities		[6]	0	[6]
Corporate Asset Backed [Member]
Variable Interest Entity [Line Items]
VIE Assets	11,481		13,028
Maximum Exposure to Loss	6,069		7,248
Investments	1	[1]	2	[1]
Premiums receivable	67	[2]	80	[2]
Insurance loss recoverable	18	[3]	18	[3]
Unearned premium revenue	82	[4]	96	[4]
Loss and loss adjustment expense reserves		[5]	0	[5]
Derivative liabilities		[6]	0	[6]
Global Structured Finance [Member]
Variable Interest Entity [Line Items]
VIE Assets	43,219		56,528
Maximum Exposure to Loss	23,967		27,379
Investments	138	[1]	141	[1]
Premiums receivable	170	[2]	196	[2]
Insurance loss recoverable	657	[3]	676	[3]
Unearned premium revenue	177	[4]	204	[4]
Loss and loss adjustment expense reserves	353	[5]	361	[5]
Derivative liabilities	96	[6]	113	[6]
Global Public Finance [Member]
Variable Interest Entity [Line Items]
VIE Assets	53,364		52,317
Maximum Exposure to Loss	20,219		20,162
Investments		[1]	0	[1]
Premiums receivable	200	[2]	206	[2]
Insurance loss recoverable		[3]	0	[3]
Unearned premium revenue	242	[4]	248	[4]
Loss and loss adjustment expense reserves	6	[5]	5	[5]
Derivative liabilities		[6]	0	[6]
Total Insurance [Member]
Variable Interest Entity [Line Items]
VIE Assets	96,583		108,845
Maximum Exposure to Loss	44,186		47,541
Investments	138	[1]	141	[1]
Premiums receivable	370	[2]	402	[2]
Insurance loss recoverable	657	[3]	676	[3]
Unearned premium revenue	419	[4]	452	[4]
Loss and loss adjustment expense reserves	359	[5]	366	[5]
Derivative liabilities	$ 96	[6]	$ 113	[6]

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

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

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

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

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

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