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Insurance Regulations And Dividends (Narrative) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
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 | 1,900 | $ 1,900 |
Statutory net loss | 64 | 28 |
Statutory capital | 88 | 152 |
Policyholders' surplus | 83 |  |
Contingency reserves | 5 |  |
Statutory net income |  |  | $ 46
National [Member] |  |  |
Insurance Regulations And Dividends [Line Items] |  |  |
Dividends from subsidiaries | 69 |  | 72
Statutory net loss | 133 | 142 |
Statutory capital | 912 | 1,100 |
Policyholders' surplus | 602 |  |
Contingency reserves | $ 310 |  |
Statutory net income |  |  | $ 75
National [Member] | S 2023 A Dividends [Member] |  |  |
Insurance Regulations And Dividends [Line Items] |  |  |
Dividends from subsidiaries |  | 550 |
National [Member] | O 2023 A Right Dividends [Member] |  |  |
Insurance Regulations And Dividends [Line Items] |  |  |
Dividends from subsidiaries |  | $ 97 |

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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 -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-3 + Details
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