Variable Interest Entities (Summary Of Nonconsolidated VIEs Assets And Liabilities) (Detail) - USD ($) $ in Millions		Jun. 30, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Insurance loss recoverable		$ 365	$ 577
Global Structured Finance [Member]
Variable Interest Entity [Line Items]
VIE Assets		23,828	28,311
Maximum Exposure to Loss		12,441	14,495
Investments	[1]	78	74
Premiums receivable	[2]	65	80
Insurance loss recoverable	[3]	358	418
Unearned premium revenue	[4]	63	78
Loss and loss adjustment expense reserves	[5]	449	418
Derivative liabilities	[6]	3	6
Global Structured Finance [Member] | Collateralized Debt Obligations [Member]
Variable Interest Entity [Line Items]
VIE Assets		3,806	5,712
Maximum Exposure to Loss		2,319	3,046
Investments	[1]	52	51
Premiums receivable	[2]	5	9
Unearned premium revenue	[4]	2	6
Loss and loss adjustment expense reserves	[5]	85	108
Derivative liabilities	[6]	3	6
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member]
Variable Interest Entity [Line Items]
VIE Assets		10,476	11,524
Maximum Exposure to Loss		5,468	6,072
Investments	[1]	21	23
Premiums receivable	[2]	30	31
Insurance loss recoverable	[3]	356	416
Unearned premium revenue	[4]	28	30
Loss and loss adjustment expense reserves	[5]	356	306
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member]
Variable Interest Entity [Line Items]
VIE Assets		280	319
Maximum Exposure to Loss		172	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		5,210	5,538
Maximum Exposure to Loss		1,458	1,712
Premiums receivable	[2]	8	13
Unearned premium revenue	[4]	7	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		4,056	5,218
Maximum Exposure to Loss		3,024	3,446
Investments	[1]	5
Premiums receivable	[2]	22	26
Insurance loss recoverable	[3]	2	2
Unearned premium revenue	[4]	26	30
Global Public Finance [Member]
Variable Interest Entity [Line Items]
VIE Assets		45,221	44,162
Maximum Exposure to Loss		13,331	14,579
Premiums receivable	[2]	145	160
Unearned premium revenue	[4]	168	186
Total Insurance [Member]
Variable Interest Entity [Line Items]
VIE Assets		69,049	72,473
Maximum Exposure to Loss		25,772	29,074
Investments	[1]	78	74
Premiums receivable	[2]	210	240
Insurance loss recoverable	[3]	358	418
Unearned premium revenue	[4]	231	264
Loss and loss adjustment expense reserves	[5]	449	418
Derivative liabilities	[6]	$ 3	$ 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.