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Outstanding Exposure - Financial Guaranty Portfolio by Internal Rating (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Aug. 31, 2023 | Dec. 31, 2022
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Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 249,153 | $ 108 | $ 233,258
% of total net par outstanding | 100.00% |  | 100.00%
AAA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 3,504 |  | $ 3,584
% of total net par outstanding | 1.40% |  | 1.50%
AA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 25,868 |  | $ 24,383
% of total net par outstanding | 10.40% |  | 10.50%
A |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 118,123 |  | $ 107,493
% of total net par outstanding | 47.40% |  | 46.10%
BBB |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 96,221 |  | $ 91,906
% of total net par outstanding | 38.60% |  | 39.40%
BIG |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 5,437 |  | $ 5,892
% of total net par outstanding | 2.20% |  | 2.50%
U.S. |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 198,921 |  |
Non U.S. |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | 50,232 |  |
Public finance |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | 239,296 |  | $ 224,099
Public finance | BIG |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | 4,402 |  | 4,777
Public finance | U.S. |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 190,289 |  | $ 179,636
% of total net par outstanding | 100.00% |  | 100.00%
Public finance | U.S. | AAA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 110 |  | $ 222
% of total net par outstanding | 0.10% |  | 0.10%
Public finance | U.S. | AA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 17,883 |  | $ 16,241
% of total net par outstanding | 9.40% |  | 9.10%
Public finance | U.S. | A |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 102,945 |  | $ 96,807
% of total net par outstanding | 54.10% |  | 53.90%
Public finance | U.S. | BBB |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 66,080 |  | $ 62,570
% of total net par outstanding | 34.70% |  | 34.80%
Public finance | U.S. | BIG |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 3,271 |  | $ 3,796
% of total net par outstanding | 1.70% |  | 2.10%
Public finance | Non U.S. |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 49,007 |  | $ 44,463
% of total net par outstanding | 100.00% |  | 100.00%
Public finance | Non U.S. | AAA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 2,062 |  | $ 1,967
% of total net par outstanding | 4.20% |  | 4.40%
Public finance | Non U.S. | AA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 3,379 |  | $ 3,497
% of total net par outstanding | 6.90% |  | 7.90%
Public finance | Non U.S. | A |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 12,968 |  | $ 9,271
% of total net par outstanding | 26.50% |  | 20.90%
Public finance | Non U.S. | BBB |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 29,467 |  | $ 28,747
% of total net par outstanding | 60.10% |  | 64.60%
Public finance | Non U.S. | BIG |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 1,131 |  | $ 981
% of total net par outstanding | 2.30% |  | 2.20%
Structured finance |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 9,857 |  | $ 9,159
Structured finance | BIG |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | 1,035 |  | 1,115
Structured finance | U.S. |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 8,632 |  | $ 8,228
% of total net par outstanding | 100.00% |  | 100.00%
Structured finance | U.S. | AAA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 867 |  | $ 926
% of total net par outstanding | 10.00% |  | 11.20%
Structured finance | U.S. | AA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 4,517 |  | $ 4,633
% of total net par outstanding | 52.30% |  | 56.30%
Structured finance | U.S. | A |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 1,639 |  | $ 1,075
% of total net par outstanding | 19.00% |  | 13.10%
Structured finance | U.S. | BBB |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 574 |  | $ 479
% of total net par outstanding | 6.70% |  | 5.80%
Structured finance | U.S. | BIG |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 1,035 |  | $ 1,115
% of total net par outstanding | 12.00% |  | 13.60%
Structured finance | Non U.S. |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 1,225 |  | $ 931
% of total net par outstanding | 100.00% |  | 100.00%
Structured finance | Non U.S. | AAA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 465 |  | $ 469
% of total net par outstanding | 38.00% |  | 50.40%
Structured finance | Non U.S. | AA |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 89 |  | $ 12
% of total net par outstanding | 7.30% |  | 1.30%
Structured finance | Non U.S. | A |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 571 |  | $ 340
% of total net par outstanding | 46.60% |  | 36.50%
Structured finance | Non U.S. | BBB |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 100 |  | $ 110
% of total net par outstanding | 8.10% |  | 11.80%
Structured finance | Non U.S. | BIG |  |  |
Schedule of Insured Financial Obligations [Line Items] |  |  |
Net Par Outstanding | $ 0 |  | $ 0
% of total net par outstanding | 0.00% |  | 0.00%

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