Retirement Benefits- Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure
Defined Benefit Plan, Service Cost	$ 1	$ 1	$ 1
Interest cost	2	3	3
Expected return on plan assets	(10)	(9)	(7)
Prior service credit amortization	1	18	24
Net periodic benefit cost	$ (6)	$ 13	$ 21