Outstanding Exposure - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Aug. 31, 2021	Jun. 30, 2022	Jul. 08, 2022	Mar. 31, 2022	Mar. 15, 2022	Jan. 18, 2022	Dec. 31, 2021
Schedule of Insured Financial Obligations [Line Items]
Loss mitigation securities and other		$ 1,200					$ 1,300
Net par outstanding		232,812					236,392
Residual value insurance policies exposure downgraded		1,625					1,605
Net Exposure		1,119					1,071
Guarantor, maximum exposure		250
Puerto Rico
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		2,227					3,572
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		1,298					2,643
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | GO/PBA PSA
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		42					1,219
Cash received net of outbound reinsurance					$ 530
Recovery bonds received, net					605
Contingent value instruments received, net					258
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | GO/PBA PSA | Assumed
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		1
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | GO/PBA PSA | Direct
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		41
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | GO/PBA PSA | Second-to-pay Exposure
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding				$ 10
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | GO
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		37					1,097
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | GO | Assumed
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		1
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | GO | Direct
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		36
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PBA
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		5					122
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PBA | Assumed
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		0
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PBA | Direct
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		5
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | HTA/CCDA PSA
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		1,256					1,408
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PRHTA (Transportation revenue)
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		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 par outstanding		457					457
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | Puerto Rico Convention Center District Authority
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		0					152
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PREPA
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		748					748
Puerto Rico | Puerto Rico Exposures Subject to a Plan or Support Agreement | PRIFA
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		0					16
Puerto Rico | Constitutionally Guaranteed | GO
Schedule of Insured Financial Obligations [Line Items]
Litigation amount						$ 35,000
Puerto Rico | Constitutionally Guaranteed | GO and PBA POA
Schedule of Insured Financial Obligations [Line Items]
Amount of outstanding principal to be paid, in percent	100.00%
Puerto Rico | Constitutionally Guaranteed | PRCCDA and PRIFA
Schedule of Insured Financial Obligations [Line Items]
Cash received for bonds					47
Notional amount of contingent value instrument received for bonds					$ 98
Puerto Rico | Pension Obligations | GO
Schedule of Insured Financial Obligations [Line Items]
Litigation amount						$ 50,000
Puerto Rico | Other Public Corporations | University of Puerto Rico
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		1
Puerto Rico | Other Public Corporations | PRASA (Puerto Rico Aqueduct and Sewer Authority)
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		1
Puerto Rico | PRHTA
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		1,300
Puerto Rico | PRHTA | Subsequent Event
Schedule of Insured Financial Obligations [Line Items]
Cash received			$ 147
Notional amount of contingent value instrument received			$ 668
U.S. Virgin Islands
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		187
Principal amount defeased		256
Principal amount upgraded (downgraded)		134
Public finance
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		224,095					227,164
Structured finance
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		8,717					9,228
Commitment to Provide Guarantees | Public finance
Schedule of Insured Financial Obligations [Line Items]
Outstanding commitments to provide guaranties		1,301
Commitment to Provide Guarantees | Structured finance
Schedule of Insured Financial Obligations [Line Items]
Outstanding commitments to provide guaranties		$ 763
BIG
Schedule of Insured Financial Obligations [Line Items]
Maximum period of liquidity claims (in years)		1 year
Net par outstanding		$ 5,386					7,356
Residual value insurance policies exposure downgraded		144					144
Net Exposure		84					84
BIG | Puerto Rico
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		2,227					3,572
Decrease in net par outstanding		1,345
BIG | U.S. Virgin Islands
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		51		$ 185			469
BIG | Public finance
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		4,091					5,972
BIG | Structured finance
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		$ 1,295					$ 1,384
Minimum
Schedule of Insured Financial Obligations [Line Items]
Probability of paying more claims than being reimbursed (as a percent)		50.00%