Employee Pension and Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Components of net periodic benefit cost
Recognized net actuarial loss			$ 49	$ 25
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	21	15	39	29
Interest cost	24	25	50	49
Expected return on plan assets	(36)	(36)	(73)	(73)
Recognized net actuarial loss	21	12	44	22
Net periodic benefit cost, Total	30	16	60	27
Other Benefits [Member]
Components of net periodic benefit cost
Service cost	3	3	6	6
Interest cost	3	3	6	6
Expected return on plan assets	(3)	(3)	(6)	(6)
Recognized net actuarial loss	2	1	4	3
Net periodic benefit cost, Total	5	4	10	9
Superannuation SERP and ESEP [Member]
Components of net periodic benefit cost
Service cost		1		1
Interest cost	1	1	2	2
Recognized net actuarial loss			1
Net periodic benefit cost, Total	$ 1	$ 2	$ 3	$ 3