Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 28	$ 28	$ 56	$ 55
Interest cost	21	25	42	49
Expected return on plan assets	(34)	(34)	(69)	(67)
Amortization of:
Prior service credit	(5)	(6)	(10)	(11)
Net actuarial loss	12	15	24	31
Net periodic benefit cost	22	28	43	57
Employee Benefit Plans (Textual)
Contributions to benefit plans			14	21
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	1	2	3	4
Interest cost	3	3	6	7
Expected return on plan assets	0	0	0	0
Amortization of:
Prior service credit	(4)	(4)	(8)	(9)
Net actuarial loss	0	0	0	0
Net periodic benefit cost	$ 0	$ 1	1	2
Employee Benefit Plans (Textual)
Contributions to benefit plans			$ 8	$ 6