Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits [Member]
Components of Net Periodic (Benefit) Cost [Abstract]
Service cost	$ 1	$ 2
Interest cost	23	29
Expected return on plan assets	(43)	(40)
Amortization of unrecognized net loss	11	11
Settlement charge	4
Net periodic (benefit) cost	(4)	2
Other Postretirement Benefits [Member]
Components of Net Periodic (Benefit) Cost [Abstract]
Interest cost		1
Expected return on plan assets	(1)	(1)
Net periodic (benefit) cost	$ (1)	$ 0