Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 35	$ 30	$ 70	$ 60
Interest cost	22	25	43	49
Expected return on plan assets	(46)	(41)	(90)	(83)
Amortization of:
Net actuarial (gain) loss	19	10	37	20
Prior service credit	(5)	(5)	(10)	(9)
Special charges	1	2	1	2
Net periodic benefit cost	26	21	51	39
Employee Benefit Plans (Textual)
Contributions to benefit plans			19	23
Future employer contributions to pension and other postretirement plans, as disclosed in annual report on Form 10-K					$ 140
Previously planned discretionary contributions subject to reconsideration	100		100
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	2	1	3	2
Interest cost	2	3	4	6
Expected return on plan assets	0	0	0	0
Amortization of:
Net actuarial (gain) loss	0	(1)	0	(2)
Prior service credit	(2)	(2)	(3)	(4)
Special charges	0	0	0	1
Net periodic benefit cost	$ 2	$ 1	4	3
Employee Benefit Plans (Textual)
Contributions to benefit plans			$ 7	$ 8
Future employer contributions to pension and other postretirement plans, as disclosed in annual report on Form 10-K					$ 21