Benefit Plans - Net Periodic Benefit Costs (Details) - Nonqualified plan - Pension plan - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2021
Net Periodic Benefit Costs [Abstract]
Interest cost	$ 3	$ 3	$ 2
Net (gain) loss recognition	5	4	(3)
Net periodic benefit cost	$ 8	$ 7	$ (1)