Stockholders' Equity - Changes in AOCI (Details) - USD ($) $ in Millions		1 Months Ended	2 Months Ended	3 Months Ended					4 Months Ended	5 Months Ended	9 Months Ended
		Jun. 30, 2023	May 17, 2023	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2023	May 17, 2023	Sep. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ 2,431		$ 2,572	$ 2,766	$ 2,534	$ 2,460		$ 2,431		$ 2,534
Other comprehensive income (loss)		(3)	$ (3)	24	(2)	(4)	(9)	$ 9	(12)	$ 6	18
Cancellation of equity at Emergence	[1]		88
Ending balance		2,460	2,431	2,445	2,572	2,766	2,358		2,358	2,431	2,445
Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		0		(29)	(27)	(23)	(3)	$ (167)	0	(167)	(23)
Gains (losses) arising during the period									(26)	6	26
Reclassifications to Consolidated Statements of Operations									7	5	(1)
Income tax benefit (expense)									7	(5)	(7)
Other comprehensive income (loss)		(3)		24	(2)	(4)	(9)		(12)	6	18
Cancellation of equity at Emergence									0	161	0
Ending balance		$ (3)	$ 0	$ (5)	$ (29)	$ (27)	$ (12)		$ (12)	$ 0	$ (5)

[1] Pursuant to the Plan of Reorganization: (i) existing equity interests were canceled; and (ii) new equity interests and equity-classified warrants were issued.