Pension and Other Postretirement Healthcare Benefits (Details) - Pensions - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net periodic cost:
Service cost	$ 1	$ 2	$ 2	$ 3
Interest cost	3	4	7	9
Expected return on plan assets	(6)	(5)	(13)	(11)
Net amortization of actuarial loss and prior service credit	1	1	2	2
Total net periodic cost	$ (1)	$ 2	$ (2)	$ 3