Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 41	$ 35	$ 81	$ 70
Interest cost	18	22	36	43
Expected return on plan assets	(48)	(46)	(96)	(90)
Amortization of:
Net actuarial loss	20	19	40	37
Prior service credit	(5)	(5)	(9)	(10)
Special charges	4	1	4	1
Net periodic benefit cost	30	26	56	51
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			31	19
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	1	2	3	3
Interest cost	1	2	3	4
Expected return on plan assets	0	0	0	0
Amortization of:
Net actuarial loss	0	0	0	0
Prior service credit	(1)	(2)	(3)	(3)
Special charges	0	0	0	0
Net periodic benefit cost	1	$ 2	3	4
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			$ 8	$ 7