Employee Benefit Plans, Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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	$ 119	$ 133	$ 123
Interest cost	98	91	86
Expected return on plan assets	(166)	(163)	(150)
Amortization of:
Net actuarial (gain) loss	41	65	53
Prior service credit	(19)	(18)	(20)
Special charges	4	7	4
Net periodic benefit cost (credit)	77	115	96
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	5	6	6
Interest cost	11	10	10
Expected return on plan assets	0	0	0
Amortization of:
Net actuarial (gain) loss	(3)	(2)	(3)
Prior service credit	(9)	(11)	(16)
Special charges	1	0	0
Net periodic benefit cost (credit)	$ 5	$ 3	$ (3)