Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8	$ 7	$ 15	$ 14
Interest cost	41	48	82	96
Expected return on plan assets	(49)	(46)	(97)	(92)
Amortization of actuarial loss (gain)	26	24	52	48
Net periodic cost	26	33	52	66
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	1	1
Interest cost	3	4	6	8
Expected return on plan assets	0	0	0	0
Amortization of actuarial loss (gain)	(4)	(5)	(8)	(9)
Net periodic cost	$ (1)	$ 0	$ (1)	$ 0