Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 28	$ 27	$ 84	$ 82
Interest cost	21	24	63	73
Expected return on plan assets	(35)	(33)	(104)	(100)
Amortization of:
Prior service credit	(5)	(5)	(15)	(16)
Net actuarial (gain) loss	13	16	37	47
Special charges (credits)	(7)	0	(7)	5
Net periodic benefit cost	15	29	58	91
Employee Benefit Plans (Textual)
Contributions to benefit plans			132	114
Discretionary contribution to benefit plans			100
Expected contributions to benefit plans in current fiscal year			136
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	2	2	5	6
Interest cost	3	4	9	11
Expected return on plan assets	0	0	0	0
Amortization of:
Prior service credit	(4)	(5)	(12)	(14)
Net actuarial (gain) loss	(1)	0	(1)	0
Special charges (credits)	0	0	0	0
Net periodic benefit cost	$ 0	$ 1	1	3
Employee Benefit Plans (Textual)
Contributions to benefit plans			$ 12	$ 11