Pension And Postretirement Plan Expenses (Summary Of Net Periodic Pension And Net Postretirement Plan Expenses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Pension [Member]
Pension And Postretirement Plan Expenses [Line Items]
Service cost	$ 20	$ 20	$ 41	$ 41
Interest cost	55	56	111	111
Expected return on plan assets	(79)	(82)	(159)	(164)
Net amortization	46	43	92	85
Total	42	37	85	73
Postretirement [Member]
Pension And Postretirement Plan Expenses [Line Items]
Service cost	0	1	1	2
Interest cost	4	5	8	9
Net amortization	(3)	(2)	(6)	(4)
Total	$ 1	$ 4	$ 3	$ 7