Financial Guarantee Insurance Contracts - Effect of Reinsurance on Premiums Written and Earned (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Written	$ (249)	$ (127)	$ (2)
Assumed Reinsurance Premiums Written	40	0	0
Ceded Reinsurance Premiums Written	(244)	(104)	(35)
Premiums written, net of reinsurance	(44)	(23)	33
Direct Premiums Earned	224	126	62
Premiums Earned, Net	78	56	47
Assumed Reinsurance Premiums Earned	18	0	0
Ceded Reinsurance Premiums Earned	164	69	15
Reinsurance on premiums earned, Net	78	56	$ 47
Reinsurance Recoverable, Allowance for Credit Loss	$ 0	$ 0