Pension & Postretirement Expenses (Summary Of Net Periodic Pension And Net Postretirement Plan Expenses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Pension And Postretirement Plan Expenses [Line Items]
Service cost	$ 19	$ 21	$ 38	$ 42
Interest cost	47	42	93	84
Expected return on plan assets	(88)	(86)	(175)	(172)
Net amortization	30	53	61	106
Total	$ 8	$ 30	$ 17	$ 60