Shareholders' Equity - Schedule of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net Of Tax [Roll Forward]
Beginning balance	$ (794)	$ (742)	$ (809)	$ (766)
Other comprehensive income (loss) before reclassification	15	(9)	9	(3)
Amounts reclassified from accumulated other comprehensive loss	11	9	32	27
Net current-period other comprehensive income (loss)	26	0	41	24
Ending balance	(768)	(742)	(768)	(742)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net Of Tax [Roll Forward]
Beginning balance	(75)	(50)	(66)	(54)
Other comprehensive income (loss) before reclassification	17	(10)	8	(6)
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net current-period other comprehensive income (loss)	17	(10)	8	(6)
Ending balance	(58)	(60)	(58)	(60)
Employee Benefit Related Adjustments
Accumulated Other Comprehensive Income (Loss), Net Of Tax [Roll Forward]
Beginning balance	(718)	(687)	(740)	(705)
Other comprehensive income (loss) before reclassification	0	(2)	1	(2)
Amounts reclassified from accumulated other comprehensive loss	11	9	32	27
Net current-period other comprehensive income (loss)	11	7	33	25
Ending balance	(707)	(680)	(707)	(680)
Unrealized Loss, net of tax
Accumulated Other Comprehensive Income (Loss), Net Of Tax [Roll Forward]
Beginning balance	(1)	(5)	(3)	(7)
Other comprehensive income (loss) before reclassification	(2)	3	0	5
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net current-period other comprehensive income (loss)	(2)	3	0	5
Ending balance	$ (3)	$ (2)	$ (3)	$ (2)