Employee Benefits (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
Retirement Plans [Member]
Components of net periodic cost for retirement plans and post-retirement plans
Service cost	$ 3	$ 16	$ 21	$ 50
Interest cost	24	25	70	75
Expected return on plan assets	(31)	(32)	(93)	(96)
Amortization of actuarial loss	8	8	24	23
Net periodic benefit cost	4	17	22	52
Post-Retirement Plans [Member]
Components of net periodic cost for retirement plans and post-retirement plans
Service cost	1	1	2	2
Interest cost	1	2	4	5
Amortization of prior service credit	0	(1)	(1)	(1)
Net periodic benefit cost	$ 2	$ 2	$ 5	$ 6