Outstanding Exposure - Additional Information (Details) $ in Millions		3 Months Ended
	Jun. 26, 2023 USD ($)	Mar. 31, 2024 USD ($) Category	Dec. 31, 2023 USD ($)	Jun. 23, 2023 USD ($)
Schedule of Insured Financial Obligations [Line Items]
Number of surveillance categories | Category		3
Loss Mitigation Securities		$ 1,200	$ 1,200
Net par outstanding		248,144	249,153
Estimated Fair Value		6,091	6,307
Fixed-maturity securities, trading		272	318
Guarantor, maximum exposure		1,500
Puerto Rico Electric Power Authority
Schedule of Insured Financial Obligations [Line Items]
Plaintiff debt capacity				$ 2,500
Plaintiff debt capacity allocated to settling creditors				1,400
Plaintiff debt capacity allocated to bondholders and general unsecured creditors				$ 1,100
Claim received as restructuring bonds, percent				12.50%
Puerto Rico Electric Power Authority | Guarantee Obligations
Schedule of Insured Financial Obligations [Line Items]
Damages sought, estimate	$ 2,400
Calculated collection period	100 years
Calculated discount rate	7.00%
Calculated discounted cash flows	$ 3,000
Additional calculated discount rate	20.00%
Damages sought	$ 8,500
Puerto Rico
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		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 par outstanding		624	624
Public finance
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		238,132	239,296
Structured finance
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		10,012	9,857
Aircraft residual value insurance (RVI)
Schedule of Insured Financial Obligations [Line Items]
Residual value insurance policies exposure downgraded		355	355
Net Exposure		200	200
Commitment to Provide Guarantees | Public finance
Schedule of Insured Financial Obligations [Line Items]
Outstanding commitments to provide guaranties		829
Potential future commitment			353
Commitment to Provide Guarantees | Structured finance
Schedule of Insured Financial Obligations [Line Items]
Outstanding commitments to provide guaranties		$ 1,800
Potential future commitment			50
BIG
Schedule of Insured Financial Obligations [Line Items]
Maximum period of liquidity claims (in years)		1 year
Net par outstanding		$ 5,193	5,437
BIG | Public finance
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		4,224	4,402
BIG | Structured finance
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding		969	1,035
BIG | Aircraft residual value insurance (RVI)
Schedule of Insured Financial Obligations [Line Items]
Residual value insurance policies exposure downgraded		144	144
Net Exposure		$ 84	$ 84
Minimum
Schedule of Insured Financial Obligations [Line Items]
Probability of paying more claims than being reimbursed (as a percent)		50.00%