Outstanding Exposure - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2025 USD ($) Category	Dec. 31, 2024 USD ($)
Schedule of Insured Financial Obligations [Line Items]
Number of surveillance categories \| Category	3
Loss mitigation securities	$ 1,200	$ 1,200
Aircraft residual value insurance (RVI)
Schedule of Insured Financial Obligations [Line Items]
Residual value insurance policies exposure downgraded	147	147
Net Exposure	87	87
Specialty business, contingent, gross par	90
Specialty business, contingent, net par	51
Aircraft residual value insurance (RVI) \| BIG
Schedule of Insured Financial Obligations [Line Items]
Residual value insurance policies exposure downgraded	5	5
Net Exposure	5	$ 5
Commitment to Provide Guarantees \| Public finance
Schedule of Insured Financial Obligations [Line Items]
Outstanding commitments to provide guaranties	2,000
Commitment to Provide Guarantees \| Structured finance
Schedule of Insured Financial Obligations [Line Items]
Outstanding commitments to provide guaranties	$ 2,200
Minimum
Schedule of Insured Financial Obligations [Line Items]
Probability of paying more claims than being reimbursed (as a percent)	50.00%