Outstanding Exposure - Puerto Rico Net Par Outstanding (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Schedule of Insured Financial Obligations [Line Items]
Net	$ 232,812	$ 236,392
Puerto Rico
Schedule of Insured Financial Obligations [Line Items]
Net	2,227	3,572
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement
Schedule of Insured Financial Obligations [Line Items]
Net	1,298	2,643
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | GO
Schedule of Insured Financial Obligations [Line Items]
Net	37	1,097
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PBA
Schedule of Insured Financial Obligations [Line Items]
Net	5	122
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | GO/PBA PSA
Schedule of Insured Financial Obligations [Line Items]
Net	42	1,219
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PRHTA (Transportation revenue)
Schedule of Insured Financial Obligations [Line Items]
Net	799	799
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PRHTA (Highway revenue)
Schedule of Insured Financial Obligations [Line Items]
Net	457	457
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PRCCDA
Schedule of Insured Financial Obligations [Line Items]
Net	0	152
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | HTA/CCDA PSA
Schedule of Insured Financial Obligations [Line Items]
Net	1,256	1,408
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PRIFA
Schedule of Insured Financial Obligations [Line Items]
Net	0	16
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PREPA
Schedule of Insured Financial Obligations [Line Items]
Net	748	748
Puerto Rico | Other Puerto Rico Exposures
Schedule of Insured Financial Obligations [Line Items]
Net	929	929
Puerto Rico | Other Puerto Rico Exposures | MFA
Schedule of Insured Financial Obligations [Line Items]
Net	179	179
Puerto Rico | Other Puerto Rico Exposures | PRASA and U of PR
Schedule of Insured Financial Obligations [Line Items]
Net	$ 2	$ 2