Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8	$ 7	$ 23	$ 21
Interest cost	41	47	123	143
Expected return on plan assets	(48)	(46)	(145)	(138)
Amortization of actuarial loss (gain)	26	24	78	72
Net periodic cost	27	32	79	98
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	1	1
Interest cost	2	4	8	12
Expected return on plan assets	0	0	0	0
Amortization of actuarial loss (gain)	(3)	(4)	(11)	(13)
Net periodic cost	$ (1)	$ 0	$ (2)	$ 0