Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 29	$ 33	$ 89	$ 100
Interest cost	25	22	74	68
Expected return on plan assets	(41)	(40)	(124)	(122)
Amortization of:
Net actuarial (gain) loss	10	16	30	49
Prior service credit	(5)	(5)	(14)	(14)
Special charges	0	2	2	7
Net periodic benefit cost	18	28	57	88
Employee Benefit Plans (Textual)
Contributions to benefit plans			120	132
Employer discretionary contributions	85
Expected employer contribution for current fiscal year	125		125
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	1	2	3	5
Interest cost	2	2	8	7
Expected return on plan assets	0	0	0	0
Amortization of:
Net actuarial (gain) loss	0	(1)	(2)	(2)
Prior service credit	(2)	(2)	(6)	(8)
Special charges	0	0	1	0
Net periodic benefit cost	1	$ 1	4	2
Employee Benefit Plans (Textual)
Contributions to benefit plans			13	$ 15
Expected employer contribution for current fiscal year	$ 21		$ 21