Employee Benefit Plans, Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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 losses are amortized	10.00%
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 109	$ 120	$ 137
Interest cost	98	91	86
Expected return on plan assets	(133)	(133)	(131)
Amortization of:
Prior service cost (credit)	(22)	(22)	(19)
Net actuarial (gain) loss	62	35	57
Special charges (credits)	7	3	(5)
Net periodic benefit cost	121	94	125
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	8	7	12
Interest cost	14	15	18
Expected return on plan assets	0	0	0
Amortization of:
Prior service cost (credit)	(18)	(18)	(14)
Net actuarial (gain) loss	0	(1)	0
Special charges (credits)	0	0	0
Net periodic benefit cost	$ 4	$ 3	$ 16