Derivative Instruments - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Value of right to reclaim cash collateral and posted margin, recorded in Other assets	$ 25,000		$ 25,000		$ 23,000
Gains in change in fair value of the call options	5,000	$ 4,000	7,000	$ 1,000
Net liability fair value of all derivative instruments linked to Ambac's own credit risk	35,000		35,000		35,000
Fair value of posted assets as collateral	53,000		53,000		50,000
Derivative assets	33,000		33,000		26,000
Variable Interest Entity, Primary Beneficiary [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative assets	216,000		216,000		226,000
Warrants [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative assets	$ 1,000		$ 1,000		$ 1,000