Employee Benefit Plans, Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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	$ 133	$ 123	$ 111
Interest cost	91	86	84
Expected return on plan assets	(163)	(150)	(139)
Amortization of:
Net actuarial (gain) loss	65	53	49
Prior service credit	(18)	(20)	(20)
Special charges (credits)	7	4	(7)
Net periodic benefit cost (credit)	115	96	78
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	6	6	7
Interest cost	10	10	12
Expected return on plan assets	0	0	0
Amortization of:
Net actuarial (gain) loss	(2)	(3)	(1)
Prior service credit	(11)	(16)	(16)
Special charges (credits)	0	0	0
Net periodic benefit cost (credit)	$ 3	$ (3)	$ 2