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, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Pension And Postretirement Plan Expenses [Line Items]
Service cost	$ 21	$ 23	$ 42	$ 45
Interest cost	42	49	84	99
Expected return on plan assets	(86)	(88)	(172)	(176)
Net amortization	53	41	106	81
Total	$ 30	$ 25	$ 60	$ 49