Variable Interest Entities (Summary Of Nonconsolidated VIEs Assets And Liabilities) (Detail) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Premiums receivable		$ 409	$ 792	$ 875
Derivative liabilities		66	88
Global Structured Finance [Member]
Variable Interest Entity [Line Items]
VIE Assets		20,088	28,311
Maximum Exposure to Loss		10,391	14,495
Investments	[1]	76	74
Premiums receivable	[2]	55	80
Insurance loss recoverable	[3]	306	418
Unearned premium revenue	[4]	52	78
Loss and loss adjustment expense reserves	[5]	406	418
Derivative liabilities	[6]	0	6
Global Structured Finance [Member] | Collateralized Debt Obligations [Member]
Variable Interest Entity [Line Items]
VIE Assets		3,167	5,712
Maximum Exposure to Loss		1,914	3,046
Investments	[1]	51	51
Premiums receivable	[2]	2	9
Unearned premium revenue	[4]	0	6
Loss and loss adjustment expense reserves	[5]	73	108
Derivative liabilities	[6]	0	6
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member]
Variable Interest Entity [Line Items]
VIE Assets		9,146	11,524
Maximum Exposure to Loss		4,796	6,072
Investments	[1]	20	23
Premiums receivable	[2]	28	31
Insurance loss recoverable	[3]	304	416
Unearned premium revenue	[4]	27	30
Loss and loss adjustment expense reserves	[5]	325	306
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member]
Variable Interest Entity [Line Items]
VIE Assets		257	319
Maximum Exposure to Loss		145	219
Premiums receivable	[2]	0	1
Unearned premium revenue	[4]	0	1
Global Structured Finance [Member] | Consumer Asset Backed [Member]
Variable Interest Entity [Line Items]
VIE Assets		4,893	5,538
Maximum Exposure to Loss		1,331	1,712
Premiums receivable	[2]	7	13
Insurance loss recoverable	[3]	2
Unearned premium revenue	[4]	5	11
Loss and loss adjustment expense reserves	[5]	8	4
Global Structured Finance [Member] | Corporate Asset Backed [Member]
Variable Interest Entity [Line Items]
VIE Assets		2,625	5,218
Maximum Exposure to Loss		2,205	3,446
Investments	[1]	5
Premiums receivable	[2]	18	26
Insurance loss recoverable	[3]	0	2
Unearned premium revenue	[4]	20	30
Global Public Finance [Member]
Variable Interest Entity [Line Items]
VIE Assets		44,306	44,162
Maximum Exposure to Loss		12,051	14,579
Premiums receivable	[2]	11	160
Unearned premium revenue	[4]	18	186
Total Insurance [Member]
Variable Interest Entity [Line Items]
VIE Assets		64,394	72,473
Maximum Exposure to Loss		22,442	29,074
Investments	[1]	76	74
Premiums receivable	[2]	66	240
Insurance loss recoverable	[3]	306	418
Unearned premium revenue	[4]	70	264
Loss and loss adjustment expense reserves	[5]	406	418
Derivative liabilities	[6]	$ 0	$ 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.