Commitments and Contingencies (Narrative) (Detail) $ in Millions	Apr. 01, 2024 USD ($)	Mar. 31, 2024 USD ($) LegalProceedings	Dec. 31, 2023 USD ($)
Commitments And Contingencies [Line Items]
Other material legal proceedings pending | LegalProceedings		0
MBIA Corp [Member]
Commitments And Contingencies [Line Items]
Other Commitment			$ 6
Amounts drawn under loan		$ 6
MBIA Corp [Member] | Subsequent Event [Member]
Commitments And Contingencies [Line Items]
Amounts drawn under loan	$ 4