Pension & Postretirement Expenses (Summary Of Net Periodic Pension And Net Postretirement Plan Expenses) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension And Postretirement Plan Expenses [Line Items]
Service cost	$ 19	$ 21
Interest cost	46	42
Expected return on plan assets	(87)	(86)
Net amortization	31	53
Total	$ 9	$ 30