Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Employee Benefit Plans (Textual)
Decrease in liability related to plan amendments			$ 328
Gain arising during the period related to plan amendments	0	0	328	0
Pension Plan, Defined Benefit [Member]
Components of net periodic benefit cost:
Service cost	35	35	71	70
Interest cost	22	23	44	46
Expected return on plan assets	(34)	(31)	(66)	(62)
Amortization of:
Net actuarial loss	15	9	29	17
Prior service cost (credit)	(6)	0	(9)	1
Net periodic benefit cost	32	36	69	72
Employee Benefit Plans (Textual)
Decrease in expected employer contributions			100
Expected future employer contributions to defined benefit plans			45
Contributions to pension plans			18	16
Other Postretirement Benefit Plan, Defined Benefit [Member]
Components of net periodic benefit cost:
Service cost	3	3	6	6
Interest cost	5	6	9	11
Expected return on plan assets	0	0	0	0
Amortization of:
Net actuarial loss	0	0	0	0
Prior service cost (credit)	(3)	(6)	(6)	(11)
Net periodic benefit cost	5	3	9	6
Employee Benefit Plans (Textual)
Contributions to pension plans			$ 8	$ 10