Variable Interest Entities Variabile Interest Entities - Carry Value of Secured Notes from LSNI (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Long-term debt	$ 508	$ 639
Ambac Assurance Corporation [Member]
Long-term debt	$ 508	$ 639

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant