Employee Benefit Plans, Components of Net Periodic Benefit Costs (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 140	$ 104	$ 88
Interest cost	93	85	83
Expected return on plan assets	(125)	(112)	(112)
Amortization of:
Prior service cost (credit)	3	2	3
Net actuarial loss	33	12	2
Net periodic benefit cost before special charges	144	91	64
Special charges (credits)	(3)	4	8
Net periodic benefit cost	141	95	72
Other Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	12	11	10
Interest cost	21	22	26
Expected return on plan assets	0	0	0
Amortization of:
Prior service cost (credit)	(23)	(23)	(20)
Net actuarial loss	1	2	4
Net periodic benefit cost before special charges	11	12	20
Special charges (credits)	0	4	0
Net periodic benefit cost	$ 11	$ 16	$ 20