Employee Benefits (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pension Plans [Member]
Components of net periodic benefit cost
Service cost	$ 29	$ 23	$ 59	$ 46
Interest cost	42	39	84	78
Expected return on plan assets	(51)	(53)	(103)	(107)
Prior service (credit) cost and transition (asset) obligation amortization	(3)	(3)	(5)	(6)
Actuarial (gain) loss amortization	32	16	63	32
Net periodic benefit cost	49	22	98	43
Postretirement Welfare Plan [Member]
Components of net periodic benefit cost
Service cost	1	2	2	4
Interest cost	2	3	4	5
Expected return on plan assets	(1)	(1)	(2)	(2)
Actuarial (gain) loss amortization	(2)	(2)	(3)	(3)
Net periodic benefit cost		$ 2	$ 1	$ 4