Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Plans, Defined Benefit [Member]
Components of net periodic benefit cost:
Service cost	$ 35	$ 28	$ 105	$ 73
Interest cost	23	21	69	64
Expected return on plan assets	(31)	(28)	(93)	(84)
Amortization of:
Prior service cost (credit)	1	1	2	2
Net actuarial loss	8	3	25	9
Net periodic benefit cost	36	25	108	64
Employee Benefit Plans (Textual)
Contributions to pension plans			132	207
Other Postretirement Benefit Plans, Defined Benefit [Member]
Components of net periodic benefit cost:
Service cost	3	4	9	9
Interest cost	5	5	16	16
Expected return on plan assets	0	0	0	0
Amortization of:
Prior service cost (credit)	(6)	(6)	(17)	(17)
Net actuarial loss	0	0	0	1
Net periodic benefit cost	$ 2	$ 3	$ 8	$ 9