Employee Benefit Plans, Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Benefit Plans (Textual)
The percentage of the higher of the projected benefit obligation or market-related value of plan assets in excess of which net actuarial (gains) losses are amortized	10.00%
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 140	$ 119	$ 133
Interest cost	85	98	91
Expected return on plan assets	(179)	(166)	(163)
Amortization of:
Net actuarial (gain) loss	74	41	65
Prior service credit	(19)	(19)	(18)
Special charges	5	4	7
Net periodic benefit cost	106	77	115
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	6	5	6
Interest cost	9	11	10
Expected return on plan assets	0	0	0
Amortization of:
Net actuarial (gain) loss	0	(3)	(2)
Prior service credit	(7)	(9)	(11)
Special charges	0	1	0
Net periodic benefit cost	$ 8	$ 5	$ 3