Benefit Plans - Postretirement Benefit Plans (Details) - Postretirement Benefit Plans - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 1
Interest cost	2	2
Net loss from experience differences	0	1
Prior service credit	0	0
Net periodic cost/(benefit)	$ 3	$ 4