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Variable Interest Entities (Summary Of Nonconsolidated VIEs Assets And Liabilities) (Detail) - USD ($) $ in Millions | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Variable Interest Entity [Line Items] |  |  |  |
Insurance loss recoverable |  | $ 530 |  | $ 511
Loss and loss adjustment expense reserves |  | 1,006 |  | 979
Global Structured Finance [Member] |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |
VIE Assets |  | 14,337 |  | 14,939
Maximum Exposure to Loss |  | 6,107 |  | 6,461
Investments | [1] | 20 |  | 19
Premiums receivable | [2] | 36 |  | 39
Insurance loss recoverable | [3] | 160 |  | 173
Unearned premium revenue | [4] | 35 |  | 37
Loss and loss adjustment expense reserves | [5] | 389 |  | 406
Global Structured Finance [Member] | Collateralized Debt Obligations [Member] |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |
VIE Assets |  | 0 |  | 0
Maximum Exposure to Loss |  | 0 |  | 0
Investments | [1] | 0 |  | 0
Premiums receivable | [2] | 0 |  | 0
Unearned premium revenue |  | 0 | [4] | 0
Loss and loss adjustment expense reserves | [5] | 0 |  | 0
Global Structured Finance [Member] | Residential Mortgage Backed Securities [Member] |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |
VIE Assets |  | 6,783 |  | 7,295
Maximum Exposure to Loss |  | 3,573 |  | 3,741
Investments | [1] | 20 |  | 19
Premiums receivable | [2] | 22 |  | 22
Insurance loss recoverable | [3] | 159 |  | 172
Unearned premium revenue | [4] | 20 |  | 20
Loss and loss adjustment expense reserves | [5] | 379 |  | 396
Global Structured Finance [Member] | Commercial Mortgage Backed Securities [Member] |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |
VIE Assets |  | 205 |  | 216
Maximum Exposure to Loss |  | 82 |  | 94
Premiums receivable |  | 0 | [2] | 0
Unearned premium revenue |  | 0 | [4] | 0
Global Structured Finance [Member] | Consumer Asset Backed [Member] |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |
VIE Assets |  | 5,089 |  | 5,010
Maximum Exposure to Loss |  | 926 |  | 981
Premiums receivable | [2] | 3 |  | 4
Insurance loss recoverable | [3] | 1 |  | 1
Unearned premium revenue | [4] | 3 |  | 3
Loss and loss adjustment expense reserves | [5] | 10 |  | 10
Global Structured Finance [Member] | Corporate Asset Backed [Member] |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |
VIE Assets |  | 2,260 |  | 2,418
Maximum Exposure to Loss |  | 1,526 |  | 1,645
Investments | [1] | 0 |  | 0
Premiums receivable | [2] | 11 |  | 13
Insurance loss recoverable |  | 0 | [3] | 0
Unearned premium revenue | [4] | 12 |  | 14
Global Public Finance [Member] |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |
VIE Assets |  | 16,065 |  | 15,568
Maximum Exposure to Loss |  | 2,493 |  | 2,524
Premiums receivable | [2] | 10 |  | 10
Unearned premium revenue | [4] | 13 |  | 14
Total Insurance [Member] |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |
VIE Assets |  | 30,402 |  | 30,507
Maximum Exposure to Loss |  | 8,600 |  | 8,985
Investments | [1] | 20 |  | 19
Premiums receivable | [2] | 46 |  | 49
Insurance loss recoverable | [3] | 160 |  | 173
Unearned premium revenue | [4] | 48 |  | 51
Loss and loss adjustment expense reserves | [5] | $ 389 |  | $ 406
[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.

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- Definition Carrying amount as of the balance sheet date of paid insurance policy claims and LAE expense expected to be recovered. + References No definition available. + Details
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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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- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
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