Outstanding Exposure - Puerto Rico Net Par Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2024	Jan. 31, 2024	Dec. 31, 2023
Schedule of Insured Financial Obligations [Line Items]
Net	$ 248,144		$ 249,153
Puerto Rico
Schedule of Insured Financial Obligations [Line Items]
Net	961		1,105
Puerto Rico | Puerto Rico Defaulted Exposures Subject to a Plan Support Agreement | Puerto Rico Electric Power Authority
Schedule of Insured Financial Obligations [Line Items]
Net	624		624
Puerto Rico | Puerto Rico Resolved Exposures Subject to a Plan Support Agreement
Schedule of Insured Financial Obligations [Line Items]
Net	228		372
Insured financial obligations, principal amount, paid down		$ 144
Puerto Rico | Puerto Rico Resolved Exposures Subject to a Plan Support Agreement | Puerto Rico Transportation Authority
Schedule of Insured Financial Obligations [Line Items]
Net	204		244
Puerto Rico | Puerto Rico Resolved Exposures Subject to a Plan Support Agreement | Puerto Rico Highways Authority
Schedule of Insured Financial Obligations [Line Items]
Net	24		128
Puerto Rico | Puerto Rico Resolved Exposures Subject to a Plan Support Agreement | PRHTA
Schedule of Insured Financial Obligations [Line Items]
Net	228
Puerto Rico | Other Puerto Rico Exposure
Schedule of Insured Financial Obligations [Line Items]
Net	109		109
Puerto Rico | Other Puerto Rico Exposure | MFA
Schedule of Insured Financial Obligations [Line Items]
Net	108		108
Puerto Rico | Other Puerto Rico Exposure | PRASA and U of PR
Schedule of Insured Financial Obligations [Line Items]
Net	$ 1		$ 1