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Variable Interest Entities (Summary Of Nonconsolidated VIEs Assets And Liabilities) (Detail) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
--- | --- | --- | ---
Variable Interest Entity [Line Items] |  |  |  |  |  |
Premiums receivable |  | $ 369 |  | $ 409 | $ 792 |
Insurance loss recoverable |  | 511 |  | 504 | $ 577 | [1]
Loss and loss adjustment expense reserves |  | 979 |  | 541 |  |
Global Structured Finance [Member] |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
VIE Assets |  | 14,939 |  | 20,088 |  |
Maximum Exposure to Loss |  | 6,461 |  | 10,391 |  |
Investments | [2] | 19 |  | 76 |  |
Premiums receivable | [3] | 39 |  | 55 |  |
Insurance loss recoverable | [4] | 173 |  | 306 |  |
Unearned premium revenue | [5] | 37 |  | 52 |  |
Loss and loss adjustment expense reserves | [6] | 406 |  | 406 |  |
Global Structured Finance [Member] | Collateralized Debt Obligations [Member] |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
VIE Assets |  | 0 |  | 3,167 |  |
Maximum Exposure to Loss |  | 0 |  | 1,914 |  |
Investments | [2] | 0 |  | 51 |  |
Premiums receivable | [3] | 0 |  | 2 |  |
Unearned premium revenue |  | 0 | [5] | 0 |  |
Loss and loss adjustment expense reserves | [6] | 0 |  | 73 |  |
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
VIE Assets |  | 7,295 |  | 9,146 |  |
Maximum Exposure to Loss |  | 3,741 |  | 4,796 |  |
Investments | [2] | 19 |  | 20 |  |
Premiums receivable | [3] | 22 |  | 28 |  |
Insurance loss recoverable | [4] | 172 |  | 304 |  |
Unearned premium revenue | [5] | 20 |  | 27 |  |
Loss and loss adjustment expense reserves | [6] | 396 |  | 325 |  |
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member] |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
VIE Assets |  | 216 |  | 257 |  |
Maximum Exposure to Loss |  | 94 |  | 145 |  |
Premiums receivable |  | 0 | [3] | 0 |  |
Unearned premium revenue |  | 0 | [5] | 0 |  |
Global Structured Finance [Member] | Consumer Asset Backed [Member] |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
VIE Assets |  | 5,010 |  | 4,893 |  |
Maximum Exposure to Loss |  | 981 |  | 1,331 |  |
Premiums receivable | [3] | 4 |  | 7 |  |
Insurance loss recoverable | [4] | 1 |  | 2 |  |
Unearned premium revenue | [5] | 3 |  | 5 |  |
Loss and loss adjustment expense reserves | [6] | 10 |  | 8 |  |
Global Structured Finance [Member] | Corporate Asset Backed [Member] |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
VIE Assets |  | 2,418 |  | 2,625 |  |
Maximum Exposure to Loss |  | 1,645 |  | 2,205 |  |
Investments | [2] | 0 |  | 5 |  |
Premiums receivable | [3] | 13 |  | 18 |  |
Insurance loss recoverable |  | 0 | [4] | 0 |  |
Unearned premium revenue | [5] | 14 |  | 20 |  |
Global Public Finance [Member] |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
VIE Assets |  | 15,568 |  | 44,306 |  |
Maximum Exposure to Loss |  | 2,524 |  | 12,051 |  |
Premiums receivable | [3] | 10 |  | 11 |  |
Unearned premium revenue | [5] | 14 |  | 18 |  |
Total Insurance [Member] |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |
VIE Assets |  | 30,507 |  | 64,394 |  |
Maximum Exposure to Loss |  | 8,985 |  | 22,442 |  |
Investments | [2] | 19 |  | 76 |  |
Premiums receivable | [3] | 49 |  | 66 |  |
Insurance loss recoverable | [4] | 173 |  | 306 |  |
Unearned premium revenue | [5] | 51 |  | 70 |  |
Loss and loss adjustment expense reserves | [6] | $ 406 |  | $ 406 |  |
[1] | As of December 31, 2017 and December 31, 2016, excludes Puerto Rico recoveries, and as of December 31, 2016, the Zohar II recoveries, which have been netted against reserves.
[2] | Reported within Investments on MBIA's consolidated balance sheets.
[3] | Reported within Premiums receivable on MBIA's consolidated balance sheets.
[4] | Reported within Insurance loss recoverable on MBIA's consolidated balance sheets.
[5] | Reported within Unearned premium revenue on MBIA's consolidated balance sheets.
[6] | Reported within Loss and loss adjustment expense reserves on MBIA's consolidated balance sheets.

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- Definition Sum of the carrying amounts as of the balance sheet date of all investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(h)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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