Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 35	$ 29	$ 105	$ 89
Interest cost	21	25	64	74
Expected return on plan assets	(44)	(41)	(134)	(124)
Amortization of:
Net actuarial (gain) loss	18	10	55	30
Prior service credit	(4)	(5)	(14)	(14)
Special charges	2	0	3	2
Net periodic benefit cost	28	18	79	57
Employee Benefit Plans (Textual)
Contributions to benefit plans			18	120
Discretionary contribution expected to make in current fiscal year	86		86
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	1	1	4	3
Interest cost	3	2	7	8
Expected return on plan assets	0	0	0	0
Amortization of:
Net actuarial (gain) loss	0	0	0	(2)
Prior service credit	(2)	(2)	(5)	(6)
Special charges	0	0	0	1
Net periodic benefit cost	$ 2	$ 1	$ 6	$ 4