Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 27	$ 30	$ 82	$ 90
Interest cost	24	23	73	69
Expected return on plan assets	(33)	(34)	(100)	(100)
Amortization of:
Prior service credit	(5)	(6)	(16)	(16)
Net actuarial (gain) loss	16	9	47	26
Net periodic benefit cost	29	22	86	69
Employee Benefit Plans (Textual)
Contributions to benefit plans			114	31
Discretionary contribution to benefit plans			77
Expected contributions to benefit plans in current fiscal year			124
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	2	3	6	6
Interest cost	4	4	11	12
Expected return on plan assets	0	0	0	0
Amortization of:
Prior service credit	(5)	(5)	(14)	(14)
Net actuarial (gain) loss	0	(1)	0	(1)
Net periodic benefit cost	$ 1	$ 1	3	3
Employee Benefit Plans (Textual)
Contributions to benefit plans			$ 11	$ 14