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Insurance Regulations And Dividends (Narrative) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Insurance Regulations And Dividends [Line Items] |  |
Percentage of policyholders' surplus | 10.00% |
Percentage of adjusted net investment income | 100.00% |
Policyholders Surplus [Member] | Minimum [Member] |  |
Insurance Regulations And Dividends [Line Items] |  |
Policyholders' surplus | $ 65 |
MBIA Corp [Member] |  |
Insurance Regulations And Dividends [Line Items] |  |
Unassigned surplus | $ (1,700) | $ 1,700
Percentage of loss reserves and unearned premium reserve required to be invested in qualifying assets | 50.00% |
Statutory net loss | $ 141 |
Statutory capital | 476 | 555
Policyholders' surplus | 282 |
Contingency reserves | 194 |
Statutory net income |  | 134
National [Member] |  |
Insurance Regulations And Dividends [Line Items] |  |
Dividends from subsidiaries | 134 | 108
Statutory net loss |  | 27
Statutory capital | 2,400 | $ 2,500
Policyholders' surplus | 1,900 |
Contingency reserves | 485 |
Statutory net income | $ 39 |

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- Definition This element represents disclosure of the aggregate cash dividends paid to the entity by consolidated subsidiaries. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04(b)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690 + Details
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