Benefit Plans - Net Periodic Benefit Costs (Details) - Nonqualified plan - Pension plan - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Periodic Benefit Costs [Abstract]
Interest cost	$ 2	$ 2	$ 3
Net (gain) loss recognition			1	$ (13)	$ (3)
Net periodic benefit cost			$ 4	$ (11)	$ (1)