Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pension Plan [Member]
Components of net periodic benefit cost:
Service cost	$ 28	$ 30	$ 55	$ 60
Interest cost	25	23	49	46
Expected return on plan assets	(34)	(33)	(67)	(66)
Amortization of:
Prior service credit	(6)	(5)	(11)	(10)
Net actuarial loss	15	9	31	17
Net periodic benefit cost	28	24	57	47
Employee Benefit Plans (Textual)
Contributions to benefit plans			21	22
Other Postretirement Benefit Plan [Member]
Components of net periodic benefit cost:
Service cost	2	1	4	3
Interest cost	3	4	7	8
Expected return on plan assets	0	0	0	0
Amortization of:
Prior service credit	(4)	(4)	(9)	(9)
Net actuarial loss	0	0	0	0
Net periodic benefit cost	$ 1	$ 1	2	2
Employee Benefit Plans (Textual)
Contributions to benefit plans			$ 6	$ 9