Outstanding Exposure - Puerto Rico Net Par Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	$ 233,258	$ 236,392
Puerto Rico
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	1,361	3,572
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	509	2,643
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement | PRHTA (Transportation revenue)
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	298	799
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement | PRHTA (Highway revenue)
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	182	457
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement | Commonwealth of Puerto Rico - GO
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	25	1,097
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement | PBA
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	4	122
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement | PRCCDA
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	0	152
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement | PRIFA
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	0	16
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement | PREPA
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	720	748
Puerto Rico | Other Puerto Rico Exposures
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	852	929
Puerto Rico | Other Puerto Rico Exposures | MFA
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	131	179
Puerto Rico | Other Puerto Rico Exposures | PRAASA and U of PR
Schedule of Insured Financial Obligations [Line Items]
Net Par Outstanding	$ 1	$ 2