Employee Benefits (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pension Plans [Member]
Components of net periodic benefit cost
Service cost	$ 30	$ 24	$ 89	$ 70
Interest cost	42	38	126	116
Expected return on plan assets	(52)	(54)	(155)	(161)
Prior service (credit) cost and transition (asset) obligation amortization	(2)	(3)	(7)	(9)
Actuarial (gain) loss amortization	31	16	94	48
Net periodic benefit cost	49	21	147	64
Postretirement Welfare Plan [Member]
Components of net periodic benefit cost
Service cost	1	2	3	6
Interest cost	3	3	7	8
Expected return on plan assets	(1)	(2)	(3)	(4)
Actuarial (gain) loss amortization	(2)	(1)	(5)	(4)
Net periodic benefit cost	$ 1	$ 2	$ 2	$ 6