XML 90 R73.htm IDEA: XBRL DOCUMENT v3.8.0.1
Postretirement Plans (Components Of Net Postretirement Benefits Expense) (Details) - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2015
Postretirement Benefit Plans [Line Items]      
Net postretirement expense $ 127 $ 95 $ 153
Postretirement Plans [Member]      
Postretirement Benefit Plans [Line Items]      
Service cost 1 1 1
Interest cost 6 8 9
Net amortization (19) (21) (22)
Net postretirement expense $ (12) $ (12) $ (12)