Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 40	$ 35	$ 121	$ 105
Interest cost	19	21	55	64
Expected return on plan assets	(48)	(44)	(144)	(134)
Amortization of:
Net actuarial loss	21	18	61	55
Prior service credit	(5)	(4)	(14)	(14)
Special charges	3	2	7	3
Net periodic benefit cost	30	28	86	79
Employee Benefit Plans (Textual)
Future employer contributions to pension and other postretirement plans, as disclosed in annual report on Form 10-K	128		128
Contributions to benefit plans			121	28
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	1	1	4	4
Interest cost	2	3	5	7
Expected return on plan assets	0	0	0	0
Amortization of:
Net actuarial loss	0	0	0	0
Prior service credit	(2)	(2)	(5)	(5)
Special charges	0	0	0	0
Net periodic benefit cost	1	$ 2	4	6
Employee Benefit Plans (Textual)
Future employer contributions to pension and other postretirement plans, as disclosed in annual report on Form 10-K	$ 22		22
Contributions to benefit plans			$ 12	$ 12